This paper presents a simple but effective method for inertial parameter identification with symmetrical trifilar pendulum and inertial measurement unit (IMU). An improvement upon conventional pendulum method is described by introducing IMU to identify the orientation of specimen by self-alignment, and then complicated equipment and experimental manipulation are not needed any more. Based on the excellent capacity of motion tracking, the IMU is also used for recording the characteristic of periodic movement by collected the information about acceleration and angular velocity. The main sources of identification errors are discussed from a set of examples. Then an experiment is carried out, and Fourier analysis is used to gain the oscillation period, which made the measurement much more convenient and accurate. The identification results are also presented by comparing with reference values computed from geometrical considerations, which proves the effectiveness of such method.