Design method for preventing backward flow of front guide mechanism, front guide mechanism and rock drill

The invention discloses a design method for preventing backward flowing of a front guide mechanism, the front guide mechanism and a rock drill, the front guide mechanism comprises a front guide shell, a bit shank, a water injection sleeve, an O-shaped sealing ring and a first lip-shaped sealing ring, and a water injection cavity communicated with a flushing channel in the bit shank is defined between the water injection sleeve and the bit shank; a water leakage early warning cavity is at least distributed at one end outside the water injection cavity, an observation hole is formed in the front guide shell, one end of the observation hole is communicated with the water leakage early warning cavity, and the other end of the observation hole is communicated with the outside of the front guide shell. The pressure difference between the pressure of the air in the water leakage early warning cavity on the flushing water in the observation hole and the pressure of the atmosphere on the flushing water in the observat