The utility model relates to a suction inlet that automatic oil feeding system of well drilling well site hay tank, low level oil tank go out oil pipe and one, no. Two oil pump links to each other, pumps mouthful to link to each other with hay tank upper portion through oil pipe on the hay tank, installs pressure sensor and solenoid valve on the hay tank on the oil pipe, inserts 220VAC after the normally open contact series connection of pressure sensor's normally open contact and the coil of solenoid valve and first contactor, one, the normally open contact with the second contactor after the coil of no. Two pump contactors is established ties with oil pump select switch respectively establishes ties, inserts 220VAC again, the normally open contact of low oil level detection switch with establish ties mutually with the coil of the normally closed interlock of high oil level detection switch and first contactor in proper order again after the 2nd normally open contact of first contactor connects in parallel after insert 5VDC, after establishing ties, the 3rd normally open contact of first contactor inserts 5VDC with the coil of second contactor. , the hay tank can mend oil by the automatic start fuel feed pump when being in low oil level, and can automatic termination of pumping when reacing high oil level.