When designing the system of the infrared (IR) small target detection, both which detection algorithm to be chosen and how to set some parameters of the detection algorithm need to evaluate the complexity of the infrared backgrounds. In this paper, an effective method to evaluate the complexity of the sea-sky infrared backgrounds based on texture analysis is proposed. According to the characteristics of Infrared backgrounds, three statistical descriptors based on gray level co-occurrence matrix are calculated, and one statistical descriptors based on edge information is calculated. All statistical descriptors are fused to evaluate the complexity of IR backgrounds finally. Real and synthetic IR images under sea-sky background are applied to validate the proposed approach. Compared to existing methods, Experimental results demonstrate the robustness of the proposed method with high performance.