Abstract: At present, there are many kinds of multi-parameter measuring instruments with the function of half-value layer(HVL) measurement in the market, which can be used to measure the HVL value of diagnostic X-ray equipment. Based on three types of multi-parameter measuring instrument, we analyze many factors that may affect the measurement of HVL, such as X-ray tube voltage, tube current, exposure time, and the placement of the HVL instrument, and then design several groups of control tests. The test results show that the deviation of the tube voltage leads to changes of the HVL and that more stable measurement results can be obtained with appropriate exposure time.