An automatic measurement and alarm system and method for tower displacement, comprises a control cabinet, measurement devices, an alarm device, and a control center. The measurement devices comprise aroller, a measuring rope, a protective cover, a sash weight, and a displacement sensor. A spiral groove is arranged in the middle of the roller. One end of the measuring rope is connected with a steel wire rope. The steel wire rope bypasses the spiral groove of the roller, and then penetrates into the opening of the upper end of the protective cover and is connected to the sash weight. Graduationis provided on the roller, and a pointer is fixed on the roller shaft, thereby measuring the angle [Alpha] between the measuring rope assembly and the horizontal. The displacement sensor measures thevertical displacement L of the sash weight. The tower horizontal offset S is calculated by the formula defined in the specification and compared with the maximum offset allowable value Smax set in the control center. The automatic measurement and alarm system and method for tower displacement which is simple in structure and low in cost, automatically calculate the displacement of the measuring rope by automatic real-time measurement, automatically calculate the tower displacement value by using the trigonometric function, realize the real-time display and alarm function, and receive little influence from the environmental and climatic factors.