The invention provides a high overload test device and method of an inertial device, belonging to the field of ground tests of inertial devices. In the high overload test device, a parachute bin, a master test bin, and a secondary bin are installed in a bomb body, the parachute bin, the master test bin and the secondary bin in a test bomb are connected in sequence, adjustable external wings are installed outside the bomb body, a parachute is stored in the parachute bin, a highly precise test combined controller is installed in the master test bin, a to-be-tested inertial measurement unit is installed in the secondary bin, a fort is installed on the ground, the fort and a port controller are connected through a cable, a shell is installed on the fort, and a matchbox and the test bomb are installed in the shell. The high overload test device and method of the inertial device realize high overload, have a long error excitation effective test range, and promote implementation of projects.The device and method adopt a simple principle, are low in cost, promote implementation of projects easily, enable multiple effective test ranges in each test, and have high test efficiency.