The invention relates to a fuel injection method for a direct injection combustion system. A spark plug and two fuel injectors of the direct injection combustion system are all located in a middle area on the top of a combustion chamber. The two fuel injectors are symmetrically arranged on the two sides of the spark plug. Fuel spray injected by the fuel injectors does not interfere with the spark plug, and the fuel spray injected by the two fuel injectors does not interfere with each other. Under the working condition that an engine operates at a large load, the two fuel injectors are controlled to conduct injection simultaneously in the air-intake stroke; under the working condition that the engine operates at a medium or small load, the two fuel injectors are controlled to conduct injection alternately or intermittently and alternately in the air-intake stroke. Under different working conditions, the flow coefficient of mist can be adjusted while the injection pressure is ensured, and the requirements of the corresponding working conditions are met.