A calibration method for a first accelerometer is disclosed. The first accelerometer is installed together with a second accelerometer in a device. The calibration method includes the second accelerometer measuring a first set of X, Y, Z accelerations in a Cartesian coordinate system, the first accelerometer measuring a second set of X, Y, Z accelerations in the Cartesian coordinate system, indicating to rotate the device, the second accelerometer measuring a third set of X, Y, Z accelerations in the Cartesian coordinate system, the first accelerometer measuring a fourth set of X, Y, Z accelerations in the Cartesian coordinate system, and calibrating X, Y, Z acceleration values measured by the first accelerometer based on the first, second, third and fourth sets of X, Y, Z accelerations.