In order to study the effect of different metal salt accelerants on the secondary ignition effect of heavy oil reservoirs, the types of combustion-supporting agent suitable for the secondary ignition of heavy oil reservoirs are further explored. By using the method of adding different metal salts to the heavy oil sands, the effects of iron nitrate and nickel nitrate in the secondary combustion of the heavy oil reservoir are studied and compared. The study results show that the addition of iron nitrate can maintain the continuous combustion of the oil sands, the fire line steadily, and the nickel nitrate can significantly shorten the induction time, thus facilitating the rapid ignition of the oil sands; The analysis of combustion exhaust gas components shows that the oil sands burn more fully after adding iron nitrate. The study clarified the mechanism and effect of two metal accelerants in the secondary ignition of fire thick oil reservoir, laid a theoretical foundation for the subsequent exploration of other types of accelerants, and is of great significance to guide the development of fire thick oil reservoir.