The　principles　and　procedures　of　TBA　method　are　described　in　detail.　A　dynamic　muti-step　finite　element　model　is　established　to　simulate　excavation　process　of　caverns　in　a　hydropower　station,　and　a　calculation　of　getting　mechanical　parameter-field　of　surrounding　rock　has　been　done　with　the　TBA　method.　The　result　is　presented　with　numerical　validation　with　GA.　The　elastic　ratio　rock　is　fixed　effectively.　The　results　show　that　the　incremental　displacements　are　consistent　well　with　those　measured　ones.　The　distribution　of　parameters　of　rock　mechanics　is　consistent　with　the　real　one.