The invention provides a blowing gas circuit and a control method for an engine gas supply system, and solves the technical problem that the existing gas blowing process is relatively high in complexity and poor in reliability. The blowing gas circuit comprises a gas delivery pipeline, wherein the gas delivery pipeline is formed between a high-pressure gas source and an exhaust port, the gas conveying pipeline comprises a balance section and a redundant section which are connected in series in sequence, the equalizing section comprises a controlled adjusting gas conveying pipeline which is connected with the high-pressure gas source in parallel, and the redundant section comprises a controlled on-off gas conveying pipeline which is connected with the balance section in parallel. The balanced regulation of the high-pressure gas is completed through the controlled regulation gas delivery pipeline of the balance section, the gas output pressure at the output side of the balance section isformed, the high and low pressure is stable and adjustable, reliable output of the pressure gas is ensured through the redundant section, so that the reliability and convenience of the gas blowing process of a low-temperature engine are ensured.