In order to get accurate time information, the GPS was always used. But GPS can not be used in outdoors due to the complicated environment. Digital zenith camera is a kind of high-precision astronomical positioning instrument. The study about time calibration based on digital zenith camera was rather little. Considering that the orientation result can be influenced by star apparent position and time. Firstly, the influence of time error and star catalogue on star apparent position was analyzed respectively. Then, the influence of star apparent position on the orientation result was analyzed. One new method of time calibration based on digital zenith camera was proposed. The precision of time calibration was 0.025 s. The analysis of experimental data shows that the time calibration method is feasibility.