China is a country with vast ocean area, long coastline and abundant marine resources. In recent years, the State Council has put forward a series of strategic plans for building a powerful maritime country, which requires to strengthen the capacity of building the omni-directional stereoscopic ocean monitoring system. On September 12, 2017, the State Oceanic Administration issued the fax about "The notice on carrying out the research on aerospace science and technology serving in marine development". It is worth mentioning that the rapid development of UAV technology has brought new opportunities to the marine application. The UAV system can be used as an important supplement method compared with satellites, ships and helicopters, which could provide a good guarantee for reconnaissance, surveillance, intelligence collection, target positioning and emergency response missions with its high reliability, high efficiency and low cost and low risk. Construction and application of ocean big data platform based on UAV system is a hierarchical architecture including application layer, service layer, access layer and resource layer from top to bottom. Every layer has its responsibility and they cooperate with each other to provide the big data service and application throughout. The platform is obviously superior to others with its diversified, comprehensive, personalized and intelligent characteristics, which can efficiently provide real-time or quasi real-time marine environment data, continuously execute missions in all-weather condition day and night, flexibly approach the accident site and immediately take emergency measures. As what is shown in picture 1, the resource layer provides a wide range of hardware, software and data resources. The access layer provides a comprehensive access means with different kinds of UAV systems, which is the core component of the whole platform. The cruise altitude of CH-AUV, CH-804C, CH-3, CH-4, CH-5 and CH-T4 is respectively 1500m in the sea, 100m~3000m,80m~6400m,200m~7200m,500m~8000m,1000m~25000m, which could fully cover of the space base, air base ,land base and sea base. The max endurance of those above is10h,4h,12h,30h,40h,30days respectively, which makes it possible to execute the missions in all-weather condition. The max payload capacity ranges from 3kg to 1050kg, so the optical, microwave and laser payloads can be carried at the same time. The service layer is a data center providing big data modeling, retrieval, association, mining and integration service where users can get these diversified services and accurate data easily at any time anywhere. The service layer provides data security for the application layer and the application layer gives feedback to the service layer according to the application requirements. These two layers supplement each other to improve the quality and efficiency of the whole platform. The application layer consists of two parts: the basic application and the integrated application. The basic application meet the basic requirements of marine applications including ocean environmental protection, disaster prevention and mitigation, maritime law enforcement, ocean and islands monitoring and emergency response. The integrated application including environmental forecast, disaster warning and situation analysis shows the high intelligence of the platform, which just describes the real smart ocean system. Above all, construction and application of ocean big data platform based on UAV system can not only provide a variety of data accessing methods, but also provide intelligent services and applications. It will bring new chapters to intelligent monitoring, dynamic prediction, systematic analysis, emergency response and other marine applications with its capacity of all directions service, all time accessing and all business coverage.