Abstract: The bolts connecting the vibration test fixtures are mainly subjected to lateral vibration load and inevitably loosen under the horizontal working condition in solid propellant motor vibration test. To address the process issues affecting the effectiveness of the test, the mechanism of bolt loosening was analyzed by an inclined slider model. Test validation was carried out through electromagnetic shocker under typical horizontal working condition of the solid propellant motor vibration test. The recommended ratio of the connection installation pre-tightening force to the test lateral load for commonly used M16 bolts was given. The results show that under the typical horizontal working condition in the solid propellant motor vibration test, to ensure the reliability of bolt connection during the vibration test (usually not exceeding 10 min), the recommended ratio of the connection installation pre-tightening force to the test lateral vibration load for commonly used M16 bolts is 12. The proposed research may provide not only a reference for the selection of bolt aperture and quantity in the fixture design for solid propellant motor vibration test but also support for the improvement of related test technology.