A photoelectric detection system based on photon counting technique is designed using photomultiplier tube (PMT) for solving the detectable problem of the ultra-weak light level in all-fiber rotational Raman lidar.In order to i mp rove the stability of the single photon pulse and the reliability of discriminat ion counting,the single photon pulse waveform is reshaped by impedance matching technique,and then the optimum selections of operational parameters such as PM T high-voltage power supply,discrimination threshold level are mainly discusse d through testing pulse height distribution in differential method,so its signal -to-noise ratio is enhanced.The experimental testing system possessing the re la tive optical intensity changeability with certainty is configured,and then the action type of pulse pileup effect and the effective dead time in this system ar e experimentally tested based on pulse pileup non-linear analysis model of Pois s on point process,so the reasonable nonlinearity correction may be adopt e d to improve its linearity.Experiment results show that this photoelectric dete ction system can implement the detection of weak optical signal whose photon cou nting rate is less than 140MHz,and its linearity is better than 1.0%.The optimized and provided experimental schemes are significant for the photoelectri c detection system of this type.