Abstract: A sensor-type flush valve assembly includes a hollow main valve body which confines an axial space with a top end portion and a lower end portion. The main valve body is formed with an inwardly and radially extending valve seat, a radial inlet port communicated with the axial space and disposed above the Valve seat, and a downwardly extending outlet port disposed below the valve seat and provided with a radial mounting hole which has an axis that is angularly spaced from that of the inlet port. The main valve body is further formed with an axially extending through-hole which extends from the mounting hole to the top end portion of the axial space. A movable valve piece is disposed in the axial space and normally blocks the valve seat. The valve piece has top and bottom sides and is formed with an axially extending water hole for guiding water from the bottom side to the top side of the valve piece.