Based on the data of ground tilt within 500 to 600 km from the epicentre of Wenchuan M8.0, Yushu M7.1, Lushan M7.0, Jiuzhaigou M7.0 and Maduo M7.4 earthquakes that occurred in the north-south seismic belt since 2000, the anomaly analysis of tidal factors, rate analysis, trend turning method, annual variation method and the change characteristics of azimuth and inclination of ground tilt data before the earthquake are carried out. The results show that the tidal factor exceeds 2 times the mean square deviation anomaly about one year before the 5 M≥7 earthquakes, and the anomaly duration is mostly 1 to 3 months. The rate analysis method is suitable for short-term anomaly index extraction, while the trend turning method and the annual variation method are more suitable for medium-and long-term prediction. The magnitude extracted by the trend turning method and calculated by empirical formula is closer to the actual magnitude. The change of dip angle and azimuth angle is more prone to quasi-synchronous anomalies in places far from the epicenter before the earthquake.As the distance to the epicenter decreases, the number of anomalies diminishes, and most of them are single anomalies in either azimuth angle or dip angle.According to the characteristics of ground tilt anomaly and magnitude prediction at present, it is considered that the entropy of ground tilt amplitude factor at present is mainly over-threshold anomaly, and the anomaly of trend turning extraction is concentrated at the junction of Gansu, Qinghai and Sichuan, and the predicted magnitude is high. The regional stress level at the junction of Gansu, Qinghai and Sichuan is still high after the Jishishan M6.2 earthquake. The distribution characteristics of the azimuth angle and dip angle of the ground tilt are similar to those observed before Wenchuan M8.0 and Lushan M7.0 earthquakes.