Abstract: To lower the computational complexity of the common parameter estimation algorithm of reconnaissance signals combined pseudorandom binary phase code (PRBC) and linear frequency modulated (LFM), a fast approach is presented. First, the square of the received signal is computed to eliminate the PRBC, then the fast dechirp algorithm is adopted to obtain the initial frequency and modulation slope, and both are used to reconstruct the LFM signal. The original signal is multiplied by the conjugated reconstructed signal to get the baseband signal of the PRBC. Finally, the code rate of PRBC is extracted by the short time integration method. Simulation and hardware implementation show that this approach has high accuracy, and the processing time is less than 0.35 ms.