In order to solve the state measurement problem of pendulum vibratio n of a suspended mass system in multimotion modes, the inclinometer sensors base d on acceleration measuring principle are introduced and the formulation of the g ain coefficients from the signal of sensor acceleration to structural pendulum a ngle is established through the theoretical analysis, which can be used to solve the measurement of planar motion of the system. Furthermore, after nonlinear mo difications, the measurement results can reach a high precision. While, similar to the motion control problem, the accelerationbased inclinometer sensor will l ose its effectiveness owing to the gyrus motion mode of the suspended structure, and the gyroscope is needed to measure the angular velocity, then the pendulum angle is acquired through mathematical integration calculations. At last, the tw o motion modes of the suspended mass system are both measured through experiment al verifications, the results of which soundly prove the feasibility and accurac y of the measuring method proposed in this paper. In addition, for the complicat ed planar and rotary coupled motion modes, the inclinometer and the gyroscope sh ould be integrated together to measure the pendulum motion state of the suspende d mass system.