Abstract: During the measurement of the dynamic laser goniometer(DLG), its very important to have a collimation device named null-indicator (NI) to establish an accurate zero point, the high speed response and the accuracy of NI are very important. This paper established an error equation of the output pulse, introduced the optical design of the auto-collimation NI and the interference NI, and obtained their errors. The accuracy of the interference NI is 0.05, the auto-collimation NI is 0.23. The interference NI can meet the precision requirement of the DLG.