Sampling is the key technology of the weak optical signal detection. However,the sampling output signal error due to the sampling clock jitter will affect the signal detection and processing. Therefore,the sampling error due to the clock jitter is analyzed when the input signal is the Gauss distribution. Accordingly,the loss of the sampling output signal-to-noise (SNR)is obtained,and the influence of the sampling bandwidth,input SNR and the signal duration on the loss of the output SNR is discussed. In the end,the effect of sampling jitter on the sampling integral detection probability is calculated with different accumulation number,which provides the guidance for the select of sampling clock in the weaken optical signal detection.