Measuring the moment of inertia of rigid body is a required item in college physics experiment in most universities. The traditional method employs the photoelectric gate and millisecond meter to measure the angular acceleration of rigid body during rotation, and subsequently obtains its moment of inertia. However, this method not only needs complex instruments, but also has low measurement accuracy. In this work, a smartphone with phyphox software has been employed to accurately measure the angular acceleration of the rigid body and then obtains its moment of inertia thanks to the high precision sensor in the smartphone. Hence, our current work evidences that smartphone exhibits high potential on improving the precision of college physics experiments with low cost, high precision, and simple operation.