The invention provides a channel blocking agent for a buried hill fractured reservoir and an injection method of the channel blocking agent. Based on 100 parts of the total mass, the channel blockingagent for the buried hill fractured reservoir comprises 34-60 parts of oil sludge, 0.2-0.5 part of a thickening agent, 0.5-1 part of a foaming agent, 1.5-2.5 parts of polyacrylamide, 0.05-0.15 part ofa regulator, 0.05-0.25 part of a cross-linking agent, 1.0-3.0 parts of volume expansion particles, and the balance of water. The channel blocking agent for the buried hill fractured reservoir has high temperature resistance and strong plugging capability, and is suitable for the buried hill fractured reservoir with large plugging difficulty. According to the injection method, the channel blockingagent for the buried hill fractured reservoir is injected into a targeted oil layer through a slug injection method; the regulation of the agent concentration of the channel blocking agent for the buried hill fractured reservoir and the usage amount of section plugs are regulated, and the reaction speed and the reaction time are controlled well, so that plugging in a deep stratum is realized.