The utility model discloses a three -jaw packing spanner belongs to high pressure plunger pump fluid end maintenance technical field. Three -jaw packing spanner for the cap is pressed to the assembly packing box, the packing spanner includes: wrench handle, including work portion and take the portion of holding, a fixed connection holds with taking in work portion, the activity of assembly part sets up in work portion, locking device sets up in work portion. The utility model discloses three -jaw packing spanner is in the adjustment or dismantle change packing box assembly rotation packing box pressure cap, and cap, the rolling disc bleeding pressure cap of can relaxing are pressed to the packing box that can be applicable to different specifications for maintenance duration shortens, and the maintenance work volume reduces and is difficult for skidding.