The drift of zero output is the main fact to impact measurement precision of the system. The temperature and nonlinearity which effect the measuremert precision the open-loop fiber optic gyro (O-FOG) are analyzed,and a novel model is presented to compensate errors caused by temperature and scale factor nonlinearity. The model is related with three factors:operate time,temperature and input angular rate. The precision can be improved by training. Experimental results show that it can eliminate effect of temperature drift and scale factor. The precision is improved in all temperature range,which shows the scheme′s feasibility.