According to the characteristics of ceilometer return noise, an effective denoising method of wavelet adaptive threshold is presented to reduce ceilometer return noise. To verify the feasibility of the denoising method, some numerical simulations are carried out to reduce the Gauss white noise of the simulated signal, and also, the laser diode ceilometer returns contaminated by noise are denoised by the method. Moreover, the comparisons among the wavelet adaptive threshold, wavelet modulus maxima, wavelet decomposing and recomposing, and the wavelet default threshold are performed. Experiment results show that the method of the wavelet adaptive threshold is capable of effectively reducing laser diode ceilometer return noise and the denoising effect is better than other three methods.