Abstract: Langgu Depression is an old area with an exploration history of more than five decades. A number of large-scale research projects have been launched, which only found a batch of relatively small oil and gas reservoirs, unable to achieve the expected results. The conversion rate of resources remains at a low level and there is still a great potential for exploration. On the basis of the second 3D seismic acquisition and joint processing of the whole depression, a new round of research has been launched including analysis of the whole structure, study of the whole sedimentary sand body, dynamic simulation of the whole oil and gas accumulations and comprehensive assessment of the whole belt. The study defines six belts and four fields as favorable exploration orientations. Daliuquan nose structural belt is selected for multi-area exploration, such as complicated faulted blocks, shallow-layer natural gas and deep conglomerate. With important results achieved, the exploration efforts led to discovery of large-scale reserves. The exploration experience and methods are of certain help and guiding significance to exploration of other old areas.