The real-time signal processing of laser pulses is one of the key technologies in the laser rangefinding. The increased ability of anti-jamming and detectable distance are the main problems to be solved. Comparing with the direct threshold detection method, digital correlation techniques offer a good possibility for improving the sensitivity of pulsed laser ranging system. The digital polarity correlation function is introduced, which can effectively reduce the hardware expended and achieve the parallel correlation computations in a single very large scale integration (VLSI) chip to increase the data throughput. Based on this digital polarity correlation system, some simulations are presented to confirm the feasibility of estimating time-of-flight from the noisy echoes, and an analysis of the influences on correlation results caused by pulse repetition rate, arrival delay, interval jitter, pulse width and sampling frequency is carried out, which provides a theory basis for laser transmitter designs used in correlation-based measurement systems.