The utility model relates to an overload protecting device of a construction hoist, which comprises pluralities of sensors and a monitor. The monitor comprises a CPU, an acquisition module, a compensating module, a keyboard, a memory, a nixie tube, an indicator lamp and a buzzer. The acquisition module and the compensating module are connected with the CPU to bidirectionally transmit data. The acquisition module is connected with the sensors and used for reading, amplifying, filtering and processing sampling values of the sensors. The keyboard and the memory are connected with the CPU to bidirectionally transmit data. The nixie tube, the indicator lamp and the buzzer are connected with the CPU, and the nixie tube displays the sampling values of the sensors. The sensors can be mounted at different positions of the construction hoist according to differences of transmission mechanisms of the construction hoist. The monitor is mounted inside a hanging cage of the hoist and performs operations such as sampling, compensating, calculating, judging, recording, outputting and the like for data of the sensors. The monitor can perform audible and visual pre-alarming or audible and visual, relay power failure alarming according to differences of loads inside the hanging cage of the hoist so as to achieve overload protecting effect, and is high in precision and fine in safety.