In order to solve the problem of multipath fading and Doppler interference in the transmission of Police Digital Trunking (PDT) signal, we proposed new diversity reception technique for PDT signal. Firstly PDT system model is given, the fading channel conditions and signal structure characteristics are analyzed at the same time. On this basis, the structure of new base band diversity technique and the key algorithm of processing procedure are proposed. Along with theoretical analysis, software simulation results are presented. The simulation results show that the proposed postdetection diversity technique provided an obvious improve of bit error rate performance for communication systems. Because of the low system complexity and computation reduction, the presented diversity structure is suitable for using in practical engineering.