The invention relates to a crankshaft journal positioning and clamping device which comprises a positioning block, a clamping rod, a spring and an adjusting screw nut, wherein a tapered long groove for accommodating a workpiece is formed in the positioning block; a column stepped hole which is communicated with the tapered long groove is formed in a side surface of the positioning block; inner threads are formed in the rear end part of the column stepped hole; the clamping rod is of a stepped column structure and is mounted inside the column stepped hole; the front end of the clamping rod contacts the workpiece; the column at the tail part of the clamping rod is sleeved by the spring; the spring is positioned between the adjusting screw nut and a boss on the clamping rod; outer threads matched with inner threads of the positioning block are formed in the adjusting screw nut; the adjusting screw nut is rotated to adjust the compression amount of the spring, so that automatic adjustment on the clamping force of the clamping rod to the workpiece can be achieved. The crankshaft journal positioning and clamping device is simple and reasonable in structure, convenient to operate and use, reliable and stable in clamping positioning, adjustable in clamping force, and is an ideal crankshaft journal positioning and clamping device.