It has been noticed that there is big systematic error with the gravity acceleration formula quoted from the 《General Meteorological Tables》,which has been using for long time in China.The gravity acceleration formula in the Guide recommended by WMO was also discussed.It pointed out that the definite of H’ with the gravity formula in the Guide is incorrect.It has been verified by examples that the gravity used with Bouguer correction is enough accurate for atmospheric pressure measurement.At the end,some pieces of suggest have been given.