Abstract: An automatic control method of inflation is revealed. An inflator including a pressure gauge with a microprocessor automatically controls an inflated object to be inflated until the pressure reaches an initial set pressure value on the pressure gauge. After the pressure reaching the initial set pressure value, an air pump of the inflator is shut down until the pressure gets balanced. Now the value shown on the pressure gauge is lower than the initial set pressure value. The difference between an actual pressure value and the initial set pressure value is calculated and is added with the initial set pressure value to get a new set pressure value the inflated object actually needs by the microprocessor. Now the inflator starts inflation again until the pressure reaches the new set pressure value. The inflation is completely precisely.