Stray light of transmission type Mie scattering lidar system is analyzed by ZEMAX software, and the reflection of optical lens surface in the lidar system and multiple reflection and scattering of the tube wall system are simulated.The power of multiple reflection light imaging on the detector surface source reaches 3×10-8 W, and the power of lens barrel light scattering imaging on the detector surface source reaches 2.8×10-9 W. Under the same measurement conditions, we analyze the continuous observation results of two kinds of laser lidars, and conclude that the echo signal strength converted from near-field stray light in the transmission type Mie scattering lidar can reach 1000 mV, which is nearly 17 times that of the reflection type lidar system. Attenuation piece is used to attenuate the two lidar signals respectively. The results show that when the signal attenuation is 80%, the near field signal of the transmission type lidar system is turned up. It can be seen from the results of nonlinear signal processing that the reflection type lidar system is better than the transmission type lidar system.