To detect structural damage degree and damage axial direction, reduce detection range and achieve accurate damage location with high efficiency and low cost, a transmission tower structural damage detection method based on MIMU was proposed. Firstly, based on the Angle of transmission tower structure, the MIMU micro-inertial measurement system is used to monitor the structure change of transmission tower, and the translation and rotation entropy matrices are constructed combined with the structural entropy. Then, the damage degree and damage axial direction of transmission tower structure are detected by using the damage index of entropy distance and variation entropy. Finally, simulation and in-service transmission towers under various working conditions are designed to verify the rationality of the algorithm. The results show that the error between the entropy distance index and the theoretical value is less than 3%, which can effectively detect the damage degree of the structure. The variation entropy index of damaged axial direction is 20% ~ 53. 9% higher than that of undamaged axial direction, which can effectively detect the damaged axial direction of structures. This method can provide a practical basis for truss structure damage detection.