The Luding M_S6.8 earthquake on September 5,2022 in Sichuan Province of China is within the potential area of the annual earthquake hazard map provided by the China Earthquake Administration. In this paper,we systematically reviewed the seismicity and geophysical observation anomalies before the shock as follows. ①The medium-term forecasting is mainly based on the anomalies of seismic gap with M_S≥4.0 in Sichuan-Yunnan-Tibet border area,the M_L≥3.5 earthquake gap near the annual earthquake hazard map,trend anomalies of across-fault deformation and gravity anomaly. The gap of M_S≥4.0 earthquake was broken by the January 2,2022 Ninglang M_S5.5 earthquake in Yunnan Province,which is of significance for medium-short term prediction. ②In the short-term stage before the Luding earthquake,the seismic gap with M_S≥4.0 earthquake experienced evolution process of broken-strengthening-quiescence,which is highly similar to that of before the 1973 Luhuo M_S7.6 earthquake in Sichuan Province. This may be related to the fact that the two earthquakes have the same seismogenic structure,focal mechanism and deep seismogenic environment. In addition,there exist some anomalies,such as the quasi-synchronous activity of the earthquake swarms and the significant seismic activity in aftershock areas in Sichuan-Yunnan region,and the Batang earthquake swarm. After the Lushan M_S6.1 earthquake on June 1,2022 and the Maerkang M_S6.0 on June 10,2022,the precursor anomalies did not decrease significantly in Sichuan Province and its surrounding areas,while the anomalies increased significantly from July to August,which can be considered as a short-term basis for predicting the next earthquake. The new appeared anomalies mainly distributed within 300km of Sanchakou area(the intersection area of the Xianshuihe fault,the Anninghe fault and Longmenshan Fault zone),which is one of the main bases for the short-term location prediction before the Luding earthquake. ③At the medium-short-term stage before the Luding earthquake,the crustal deformation anomalies with large amplitude are remarkable. These anomalies are in the range of 130～300km around the epicenter of the Luding earthquake except for the Lizhou baseline,the other anomalies are located outside the seismic gap with M_L≥3.5. The occurrence time of the crustal deformation anomalies is roughly consistent with the significant enhancement of seismic activity in the gap and nearby. ④The Luding shock occurred in the Sanchakou area,which region and its vicinity has been identified as the potential area of the annual earthquake hazard map from 2015 to 2021,but there was no predicted event occurred. This suggests that the time prediction index for medium-term is not sufficient.