The invention discloses a fixture for grinding the ball end of a plunger connecting rod assembly. The fixture comprises a clamping plate which consists of a first clamping plate and a second clamping plate, wherein the first and the second clamping plates are respectively formed by cutting a hollow cylinder by two parallel planes from the center to two sides, the two ends of the first and the second clamping plates are further provided with arc-shaped tables matched with a connecting rod on a plunger ball end and a plunger sleeve. The fixture can clamp a machine tool chuck, the clamping plates and the connecting rod of the plunger ball end, prevents the ball end from rotating relative to the plunger sleeve and a machine tool chuck in the grinding process, is simple in structure and convenient to use, solves the problem that the ball end of the plunger connecting rod assembly can not be ground, increases the grinding efficiency of the ball end, and fundamentally guarantees the assemblyprecision of the ball end.