The utility model discloses a spill -over valve is prevented to active oil discharge, including the main valve, connect the last valve pipe and the connection of main valve upper end are in the lower valve pipe of main valve lower extreme, the main valve includes the valve body, installs float, setting in the valve body outer peripheral edges recess are in just be located on the valve body inner wall the pawl of float below and with pawl matched with valve block subassembly, the float passes through the pull rod and links to each other with the pendulum rod, the axle that the pendulum rod passes through on the pendulum rod rotates continuously with the pawl, the float passes through the pull rod and drives the pendulum rod rotates, the rotation of pendulum rod drives the rotation of pawl, the rotation of pawl realize with the unblock of valve block subassembly. The utility model has the advantages of simple structure, the function is turn -offed to simple to operate, reliable initiative shutoff and the two -stage of just can realizing of function to automatic re -setting when the liquid level descends, used repeatedly many times reduces the probability of occurence of failure.