Abstract:When a hydraulic excavator was working under a given load, the import and export pressures of the operating cylinder were tested by the comprehensive features portable pressure & flow meter. The test results were imported into MATLAB,and the dynamic change curves of the pressures were drawn. Combining fluid mechanics theory with the cylinder pressure curves, the pressure losses before and after the oil cylinder were analyzed. According to the time span from brake to stable state, the stability of the cylinder was evaluated. The problems needed to improve and pay attention to were pointed out.