The main factors are analyzed,which causes the speech communication distortion in circuit designing of the laser atmospheric speech communication: the selection of A/D converter and the baud rate setting. In experiments,it is testified that the higher conversion accuracy of A/D converter is required to guarantee the speech communication quality,the A/D conversion accuracy should be more than eight bits,and conversion velocity is relatively lower required,speech singles sampling speed is usually chosen 8 kHz and 10 kHz. When the right coding mode is chosen,baud rate should be set more than digital signals transmission velocity,and the speech communication quality can be guaranteed.