Abstract: Pseudorandom modulation rate which used to modulate 1 550 nm fiber laser was prompted from 622 MHz to 1 GHz in the laser ranging system based on high speed pseudorandom modulation and photon counting technology. Ranging performance was compared and demonstrated under two different modulation rates using the optical fiber delay method. 10 order M-sequence pseudorandom code and the same InGaAs/InP single photon detector with detection efficiency of 10% were implemented in the system. Under condition of input signal average energy of 1.9410-17 J, the similar SNRs were acquired in the two systems and the ranging accuracy was improved by 1.58 times under high modulation rate which was in good agreement with theory result. The actual ranging platform was established and ranging experiment was carried out indoor. The ranging accuracy of 2.1 cm was obtained when measuring a high-reflected target which was about 4.5 m away. The result is useful for outdoor ranging system.