A rotary impact assembly structure includes a rotary tool and a rotary impact assembly. The rotary tool is assembled with the rotary impact assembly so that the rotary impact assembly is driven by the rotary tool to rotate. The rotary impact assembly has a counterweight plate. The counterweight plate has a first surface and a second surface at two sides thereof. The first surface is provided with a socket portion having an insertion hole at a center thereof. The second surface is provided with a plug portion at a center thereof. The rotary impact assembly structure is able to increase the rotational inertia and the amount of torque to quickly loosen or tighten a fastener and has a simple and convenient operation.