Fully automatic biochemical analyzer is used for quantitative analysis and detection of specific substances in blood and urine, but frequent use causes frequent failures. We summarized the causes, troubleshooting and maintenance results of four faults in Toshiba TBA-120FR analyzer. The working principle of the automatic biochemical analyzer was analyzed. Several malfunctions were solved, including unable to absorb the reference liquid, low test results of the patient samples, the cross contamination of the sample results, and poor reproducibility of the results. Moreover, the device was guaranteed to be used normally after troubleshooting. We also hope that the mentioned maintenance cases can provide reference for industry workers to repair faults of similar equipment.