Abstract: To quickly predict the coverage performance of radar and mobile base station in three-dimensional complex environment, a fast algorithm of SSFT for three dimensional parabolic equation is proposed, and the specific formula derivation is given. Firstly, the results of fast algorithm are compared with two-ray model and the existing approach of decomposing the field into odd and even parts, it shows that the fast algorithm is in good agreement with the other two methods, and the calculation speed is promoted nearly 1. 61 times compared with the approach of decomposing the field into odd and even parts, which verifies the correctness and efficiency of fast algorithm. On this basis, the electromagnetic attenuation characteristics of radar in complex marine environment are simulated, and the radar detection blind area is discussed, which will provide theoretical reference for the evaluation of radar detection performance in complex environment.