Abstract: As the core support structure of power system, the safety and stability of transmission tower is directly related to the reliable operation of power grid. In this paper, a 1A4X-ZMC5 typical cat-head-shaped transmission tower is taken as the research object, and the coupled effects of strong wind, ice-covering and gravity load are considered comprehensively to establish a finite element model and carry out modal analysis and multi-condition static mechanic research. By applying the combination of gravity, wind and ice loads, the key mechanical response law of the structure is revealed. The results show that the maximum strain value occurs at the 16.6 m height angle steel during installation. Based on this, strain monitoring points are set and a two-level early warning threshold is established, with a yellow warning of 928 με and a red warning of 1 238 με. The peak horizontal displacement of the top of the tower reaches 518.67 mm, and based on the displacement control requirements, the tower top monitoring program and graded warning indicators are proposed: the yellow warning threshold is 311.2 mm, and the red warning threshold is 414.9 mm. This provides a theoretical basis and engineering reference for the service safety assessment and early warning threshold setting of cat-head-shaped transmission towers.