The invention provides an engine blowdown gas circuit. The engine blowdown gas circuit comprises a high-pressure gas source input end, a reducing valve, a first normally-open two-position three-way electromagnetic valve, a first two-position two-way electromagnetic valve, a second two-position two-way electromagnetic valve, a third two-position two-way electromagnetic valve, a fourth two-position two-way electromagnetic valve, a first restriction orifice, a one-way valve, a second normally-open two-position three-way electromagnetic valve, a gas supply output end, a first blow-off end, a low-pressure gas source input end, a fifth two-position two-way electromagnetic valve, a second restriction orifice, a sixth two-position two-way electromagnetic valve and a third restriction orifice. According to the engine blowdown gas circuit provided by the invention, the gas circuit is provided with the high-pressure gas source input end and the low-pressure gas source input end, so that high-pressure blowdown gas supply and low-pressure blowdown gas supply are achieved, and realization is easy; due to the redundancy design of the gas circuit, when gas supply valves have a single fault, the blowdown gas supply function is ensured, and the high-reliability gas supply requirement can be met.