Activated heavy oil is a favorable blocking agent, because of its good selectivity and recyclability. In this paper, by simulating the reservoir conditions of Tahe Oilfield, the feasibility of water shutoff by activated heavy oil for high temperature, high salinity and high hardness reservoirs has been studied. Based on the reservoir characteristics, a nonionic-anionic compound emulsifier of 2 % MZ-18 + 3 % BH-12 (MZ-18 = nonionic amide emulsifier condensed by long chain carboxylic acid and polyethylene polyamine; BH-12 = anionic sulfonate emulsifier) was screened out as the optimum emulsification system for the activated heavy oil. The W/O emulsion prepared by the activated heavy oil is of high viscosity; besides, its temperature resistance, salinity tolerance and thermal stability were competent to Tahe reservoir. The water shutoff performance of activated heavy oil was evaluated by the physical simulation experiments. The results show that the activated heavy oil can improve the water shutoff performance and flushing resistance performance in a wide range of permeability – from 300 to 1 500 mD. Also it is found that, the water shutoff ability of the activated heavy oil increases with the increase of permeability of the sands, injection rate of blocking agent as well as the displacing rate of displacement fluid.