A battery internal pressure tester with high performance pressure sensors,matching package structure and data collecting and storing software and hardware has been developed. This system is applicable to batteries with either aqueous or organic electrolyte. With high precision，it can determine battery internal pressure quantitatively . Meanwhile，it is simple to handle and responds quickly，which makes it possible for in situ measurement of a battery’s internal pressure.In the test of a nickel metalhyoride(MHNi) batteries，results show that there is a linear relationship between stable internal pressure and state of charge. Li4Ti5O12/LiCoO2 and Li4Ti5O12/LiMn2O4 18650 type batteries have also been investigated，and a quantitative description of the gassing behavior has been given.