The utility model relates to trailer wheel hub technical field, concretely is a trailer wheel hub anti -drop connecting device, including hydraulic jack, the utility model uses, first will connect seat to be in trailer wheel hub center, make three fixed links align wheel hub center hole position, three expansion clamps go into wheel hub center hole inside, this time press the rod of hydraulic jack, the output end of hydraulic jack pushes connect seat and moves down, and fixed link drops along with it, at this moment, the pull ring fixed on the thimble draws fixed ring through chain, drives connecting shaft and support to move, makes expansion clamp rotate around convex axle, gradually expands to the outside, firmly holds the edge of wheel hub, along with the continuous press of hydraulic jack, the clamping force of expansion clamp is increasing, until the wheel hub is connected stably, when disassembling, reverse operation hydraulic jack, make its output end retract, chain slack, expansion clamp rotates inwards under the action of gravity, loosens wheel hub, can dismantle easily.