The invention provides a water inlet control method for high-temperature and high-pressure condensed water of flash evaporation groove. It is characterized in that: the needle adjusting valve and porous plate are combined to adjust the amount of condensed water; the end of water inlet tube is mounted with porous plate; the center of bottom of flash evaporation groove is mounted with impact-against sombrero; the porous plate is towards to said impact-against sombrero; and it vertically feeds water that the high-temperature and high-pressure condensed water out from the porous plate is injected to the impact-against sombrero. The invention can reduce the consumption of high-pressure steam, save energy, prolong the service life of flash evaporation groove, improve the safe parameter and reduce the noise.