For enhancing the veracity of interferential detection and reducing algorithms power and complexity, we introduce interferential detection technology based on FFT, calculate the Stat. in frequency and set the gate limit θ*a. Adjudicator compare the Stat. and gate limit and output the information about existence of interfere. The feasibility of algorithms is verified by simulation. The algorithm is easy to realize on chip, and steps up interferential detection performance of miniaturization satellite navigation terminal.