Abstract: "One plane and two pins" positioning is the most common mode of workpiece-fixture positioning and fixture-machine tool positioning. This paper introduces the design characteristics of an adjustable "one plane and two pins" positioning device, which can be used to connect the positioning pin with the machine tool fixture through the positioning pin base. The positioning device is also position-adjustable, facilitating optimized location of the positioning pin. Compared with the fixed "one plane and two pins" positioning device, this device features much greater operability, superiority and compatibility in the design and application of special fixtures, and can compensate and correct for the positioning error of fixtures to effectively eliminate the impact of various positioning errors, thereby improving the positioning accuracy of one plane and two pins positioning, and maximizing the positional precision of workpiece processing.