The invention discloses a liquid injection flow channel, and belongs to the technical field of MEMS processes. The liquid injection flow channel comprises a substrate layer, a cavity wall layer and a spray hole layer, wherein an ink inlet channel is formed in the middle of the substrate layer, a pressure cavity is formed in the cavity wall layer, spray holes are formed in the spray hole layer, the cavity wall layer and the spray hole layer are sequentially arranged on the substrate layer, the pressure cavity communicates with the ink inlet channel and the spray holes respectively, and the cross section of the ink inlet channel is in a curve shape, the substrate layer comprises a substrate rectangular part, substrate extension parts a and substrate extension parts b, the multiple substrate extension parts a are arranged on the two sides of the substrate rectangular part in the width direction respectively, and the substrate extension parts b are arranged at the two ends of the substrate rectangular part in the length direction respectively. According to the liquid injection flow channel, the printing quality is better, the printing precision is higher, ink is supplied in time, a runner can be completely filled, and the ink jetting quality is improved.