The Bragg frequency, which describes the upper limit frequency of distributed phase shifters, is a very important parameter of RF distributed MEMS phase shifters. This paper discusses in detail the underlying cause and analysis method of Bragg frequency. In addition, by using microwave network theory, the Bragg frequencies of MEMS phase shifters with different dimensions have been calculated. The simulated results demonstrate the Bragg frequency is decreased by increase of the dimension and spacing. The studied phase shifters consist of a CPW line (50 Ω) periodically with MEMS bridges at a spacing of 300 μm. When the widths of the center conductor are chosen to be 50 μm and 100μm, the Bragg frequency are 38.1 GHz and 27.6 GHz, respectively. As the width of the center conductor is fixed at 100 μm, the Bragg frequency reduces form 27.6 GHz to 19.6 GHz with the spacing increasing form 300 μm to 567 μm. Researching the Bragg frequency will benefit the design and optimization of the distributed MEMS phase shifters.