OADM is a key component in DWDM due to many merits such as good performance in low loss, low price, simple and flexible integration structure. One of the critical issues focused on the research of OADM is to design multiplexer/demultiplexer hoping to reduce the insertion loss and improve the propagation efficiency of the total device. In this paper, we present the design of 4×1 and 8×1 multiplexers based on SOI materials. The devices show several advantages including low insertion loss, phase-insensitiveness, polarization independence and compact size. The devices' performances are simulated under different conditions and all exhibit satisfying results. It's ideal to equip them in compact optical system.