Chemical ignition method for in-situ combustion

The invention provides a chemical ignition method for in-situ combustion. The method includes the steps that sodium nitrite, ammonium nitrate, a combustion improver and formamidine disulfide dihydrochloride are evenly mixed, so that a mixture is acquired and coated with water soluble capsules, the diameter of each water soluble capsule is 0.2 to 0.5 time that of a stratum pore throat, dissolution is conducted for 48 h to 72 h, and a capsule mixture is acquired; after being mixed, oil and the capsule mixture with the volume ratio being 1:1 are injected in an oil layer; clean water is injected in a stratum for replacement and pushed by 0.2 m to 0.5 m; air is injected in the stratum, air injection is stopped when the capsules of the capsule mixture are broken, and the oil layer is heated through heat emitted when the capsules of the capsule mixture are broken; air is injected continuously and chemical ignition for in-situ combustion is finished, wherein the thickness of the oil layer ranges from 5 m to 20 m. According to the chemical ignition method for in-situ combustion, oil reservoir excitement can be effectively reduced, the ignition effect is improved, and the method is suitable for a heavy oil reservoir after huffing and puffing are conducted.