To address the problems of false and missed alarms caused by smoke interference in pulsed laser proximity detection, according to Mie scattering theory and the Monte Carlo method, this study established a pulsed laser proximity detection model, simulated a 905-nm pulsed laser to obtain echoes of large and small targets under the conditions of no interference and smoke interference, and analyzed the waveform characteristics of the echoes. The results show that there is a negative correlation between the distance from the transmitting and receiving system to the target and the echo amplitude without interference. The rising rate of the echo front of large and small targets increases. Under the condition of smoke interference, the pulse widths of the smoke and target echoes have a certain broadening compared with the transmitted laser waveform. However, the broadening degree of the former is greater than that of the latter, and the smoke echo waveform is asymmetric with a steep front edge and gentle back edge. The results provide a theoretical basis for anti-smoke interference in laser proximity detection.