The invention discloses a fuel injector. The fuel injector is provided with an upstream bearing plate (11), a downstream bearing plate (12) and multiple pre-mixing pipes (13). Fuel gas (F) is guided into the inner side of the upstream bearing plate and is in a gradual-diameter-expanding conical barrel shape, the downstream bearing plate (12) and the upstream bearing plate (11) jointly form a cavity in the inner side, the pre-mixing pipes (13) are borne on the downstream bearing plate (12) and the upstream bearing plate (11), and air is guided into the pre-mixing pipes. The pre-mixing pipes (13) are separably arranged at equal distances on multiple round columns, and fuel guide holes (13a) are formed in the positions, located in the cavity, of the pre-mixing pipes (13).