The planetary boundary layer (PBL) observation system developed in Dali National Climate Observatory is introduced, and the system failures were analyzed and summarized which occurred since the operation. The analysis method applicable to the partial failure of PBL observation system characteristics is proposed, which can effectively improve the diagnosing efficiency of equipment faults and unusual data, and be good for the integrity of data collection, reliability and accuracy. The method can be used as references for maintenance of PBL observation system.