The invention relates to the technical field of vehicle part machining, in particular to an automatic positioning and clamping tool for front axle plate spring installation holes and a positioning and clamping method. A front axle placing and jacking mechanism comprises clamping areas which are arranged on the two sides of a front axle and defined by two concave vertical plates. An oil cylinder is arranged between the two concave vertical plates, so that the front axle leaves the contact surfaces between the front axle and bearings and is jacked upwards. Square holes are formed in the tops of the concave vertical plates, drill plates can enter the square holes or exit from the square holes, and the width of the square holes is larger than the thickness of the drill plates. The two drill plates on the two sides of the front axle enter the square holes of the concave vertical plates or exit from the square holes of the concave vertical plates through pushing mechanisms so as to open or close the tops of the clamping areas. Through the measures of synchronous connecting rod clamping, limiting and positioning of all movements in clamping and final three-dimensional all-direction fixing adopted in tool design, the installation hole machining precision (including the transverse and longitudinal symmetry degree and hole distance of the installation holes) can be effectively guaranteed, and the installation holes can meet the requirement for final use quality.