The invention relates to a heat radiator with an air pump separate type thermosiphon for a machine room or machine cabinet, which belongs to the technical field of heat exchange of heat radiators. The heat radiator comprises an evaporator (1), a condenser (4), a liquid collecting pipe (6), a steam pipe (2), an air pump (3) and a liquid storage bend (5), wherein the condenser (4) is positioned on the upper part of the evaporator (1), the upper part of the evaporator (1) is communicated with the condenser (4) by the steam pipe (2) and the air pump (3), the bottom of the evaporator (1) is communicated with the bottom of the condenser through the liquid collecting pipe and a liquid storage bend, a seal space is formed in the hear radiator, and liquid working media are filled into the seal space. After the evaporator absorbs heat, the internal liquid working media in the seal space are gasified, steam is transmitted to the condenser by the air pump through the steam pipe, the liquid working media change into liquid after radiating heat to air around in the condenser and flow back to the evaporator through the liquid storage bend and the liquid collecting pipe, and thus, the heat radiator can radiate internal heat of a seal machine room to the atmosphere, increases the steam power of the working media and the utilization ratio of the condenser and has better heat radiating performance in a larger heat radiating range.