A　method　for　assessing　a　main　impact　parameter　of　bolt　loosening　in　a　vibrating　work　condition　and　for　loosening　mitigation,　　comprising　the　following　steps　:　　(1)　load　amplitude,　　vibration　frequency,　　and　initial　fastening　torque　can　be　selected　as　three　major　test　impact　factors　on　the　basis　of　influencing　parameters　of　bolt　loosening　in　a　vibrating　work　condition;　　(2)　by　means　of　a　quadratic　universal　rotation　combination　of　the　three　factors　and　five　levels,　　20　combinations　of　different　values　of　three　major　impact　parameters　are　designed　for　testing;　　(2)　a　target　function　for　bolt　clamping　force　decay　rate　having　three　dependent　variables　on　the　basis　of　the　quadratic　universal　rotation　combination　and　of　a　quadratic　regression　analysis　principle;　　(4)　various　coefficients　of　the　target　function　are　calculated　to　produce　a　quadratic　regression　model　on　the　basis　of　the　test　result　of　the　20　combinations　of　different　values　of　the　three　major　impact　parameters;　　(5)　in　order　to　determining　the　reliability　of　the　regression　model,　　a　variance　analysis　is　performed　with　respect　to　the　test　result,　　then　a　lack-of-fit　test　and　a　statistical　test　are　performed　with　respect　to　a　regression　equation;　　and,　　(6)　the　most　important　impact　parameter　of　bolt　loosening　in　the　vibrating　work　condition　and　the　impact　ratio　of　the　impact　parameters　with　respect　to　bolt　clamping　force　decay　are　obtained　by　analysis,　　and　lingo　is　utilized　to　optimize　the　three　major　impact　parameters　and　to　produce　the　optimal　value　for　mitigating　bolt　clamping　force　decay.