Abstract: The test of high-pressure isothermal adsorption of coal uses modern laboratory equipment to simulate seam original storage temperature and makes asorption study of balanced pressure points. But, constant temperature system in the simulation of coal seam storage temperature has volatility of 0.3 ℃. The pressure, monitored by pressure monitor system, appears inverted V-shaped cycle fluctuations caused by instability temperature, which leads to systematic errors of the final test results. Based on high pressure isothermal adsorption test standard method, the paper established the error verification test of measuring constant temperature system and the pressure sensor. According to the adsorption test results from Dingji Coal Mine 11-3 seam of Huainan Mining Area, the paper verify the error range of pressure monitoring system on the high-pressure isotherms adsorption test of coal.