The satellite ground station receiving system is based on the incomplete case library in Case-Based Reasoning(CBR). The computation based on Fault Tree Analysis(FTA) is complex. A joint fault diagnosis method based on CBR and FTA is proposed. Firstly，an improved method based on quadratic retrieval strategy is proposed to solve the problem of low retrieval efficiency. Then，re-use the fault tree diagnosis on the fault which cannot be retrieved in the case library，and add the successful cases of fault tree analysis and processing to the case library and continuously improve the case library. Finally，based on the practical application of fault diagnosis of local oscillator equipment in satellite terrestrial stations，the fault which was not included in the case library is correctly diagnosed and the number of cases in the case library is increased, the retrieval efficiency is improved. The effectiveness of the proposed method is verified.