The utility model discloses a bridge pile foundation's detection device of resistance under water, including the sleeve, the sleeve is the cylinder structure, telescopic one end is equipped with the toper export, install the one end of bracing piece on the telescopic inner wall, and the bracing piece is perpendicular with telescopic inner wall, the other end of bracing piece is connected with the mounting box, and the bracing piece is perpendicular with the outer wall of mounting box, the mounting box is the columnar structure, mounting box and the same axle center of sleeve, which comprises a sleeve, install the bearing on the bearing frame, the bearing frame is kept away from one side of the bottom of mounting box and is installed the 2nd sensing element, circle the one end of installing the pivot in the bearing, a sensing element is installed to the side of pivot, spiral impeller is installed to the other end of pivot, open one side of mounting box is equipped with the end cover, be equipped with sealed the pad between end cover and the mounting box, the end cover all is equipped with the through -hole with the sealed side that fills up. The installation is simple, and it is very convenient to operate, and it is accurate to measure, can obtain long -term measurement parameter.