Continuous measurements of solid particle contaminant and water content could be realized by sensors installed in hydraulic system of equipment.Due to the operating temperature and pressure of hydraulic systems were high,measurement results of sensors were easily affected.The factors influencing measurement of particle sensor were discussed and a calibration method of humidity sensor was brought out based on the curve of relative humidity and absolute humidity.Results show that flow rate and system pressure have influence on the measurement of particle sensor,while temperature change has no influence between 40 ℃ and 80 ℃.The error range of water content measurement can be limited to less than 5% based on the curve of relative humidity and absolute humidity,which meets the requirement.