The invention relates to the field of engineering construction, in particular to a temporary isolating device for construction. The temporary isolating device comprises semi-conical bending plates, bottom plates, semi-cylindrical plates, connecting belts, an alarm device body, infrared sensor device bodies and a switch; the semi-conical bending plates are in semi-conical hollow shapes; the bottom plates are arranged at the bottoms of the semi-conical bending plates; the semi-cylindrical plates are fixed at the upper ends of the semi-conical bending plates; the semi-cylindrical plates are in semi-cylindrical hollow shapes and are connected through the upper and lower connecting belts; the infrared sensor device bodies are arranged in the middles of the front sides of the semi-cylindrical plates; the alarm device body is arranged on the lower portion of the first semi-conical bending plate; and the switch is arranged on the alarm device body. The temporary isolating device is easy to carry and fix, the whole device is light, portable and convenient to carry, after placement, weights can be placed on the bottom plates to take the fixing effect, the infrared sensor device bodies can motivate warning of an alarm after a person breaks in, the effect of security warning is achieved, and practicality is high.