The utility model relates to an oil exploitation equipment utensil technical field, concretely relates to oil well automatic sampler. An oil well automatic sampler, includes that the main part is the three -way pipe of " T " type, and this three -way pipe includes mutually perpendicular and swing joint's horizontal pipe and vertical duct, transversely manages both ends and is equipped with the screw thread, is equipped with floater formula check valve and valve on the vertical duct, and the distance between floater formula check valve and the horizontal pipe is greater than valve to the distance between the horizontal pipe, the vertical duct still is connected with the auxiliary tube, and one end swing joint that the auxiliary tube deviates from the vertical duct has a closing cap, the inside collection system that is equipped with of auxiliary tube. The utility model discloses in use installs it on the oil well goes out oil pipe, opens the valve, no matter crude oil extraction when the homoenergetic enters into collection system through floater formula check valve when the extraction inside, and the condition against the current can not appear. In the time of need not sampling, it can to close the valve. Need the personnel of taking a sample not wait for the crude oil extraction constantly and cause the manpower extravagant.