The invention relates to a safe falling protector of elevators or construction lifters. An active type falling protector is characterized in that an electromagnet coil 9 of the falling protector is connected with a hoisting motor in parallel, when the elevators or the construction lifters are in a static state, a rack 5 of the falling protector drives small gears 4 under the effect of a reset spring 14, the small gears 4 drive eccentric clamping wheels 3 to clamp guide rails 15, and at the moment, the guide rails 15 are tightly clamped by the falling protector. Only after the hoisting motor is power on and started, the electromagnet coil 9 can act and pulls an armature 10, the armature 10 drives a pull bar 7 which pulls the rack 5, the rack 5 drives the two small gears 4 drive the two eccentric clamping wheels 3, the two eccentric clamping wheels 3 are in reversed rotation, so that the clamping wheels 3 are in an opened state, and the elevators or the construction lifters can freely operate up and down. When the elevators or the construction lifters operate in an overloaded mode, people in the elevators or the construction lifters can shut down a power source of a master starting contactor through a button, so that the electromagnet coil 9 of the falling protector is enabled to loss power, the rack 5 enables the eccentric clamping wheels 3 to tightly clamp the guide rails 15 under the effect of the spring 14, and accordingly an active falling protecting effect is achieved, and occurrence of major accidents of casualties is avoided.