The　theoretical　simulation　and　experimental　methods　related　to　Long　Lived　Fission　Product　(LLFP)　of99Tc　and129I　transmutation　in　nuclear　spent　fuel　were　studied　in　order　to　develop　the　feasibility　research　on99Tc　and129I　transmutation　in　XAPR　reactor.99Tc　and129I　ACE　format　cross　libraries　in　XAPR　were　generated　by　NJOY　code　based　on　ENDF/B　VII.0　library,　different　parameters　were　analyzed.　MCNP　code　was　used　to　modify99Tc　and129I　capture　cross　sections　by　adopting　new　generating　ACE　format　and　CINDER＇90　cross　sections　of　63　groups.　Transmutation　rates＇　calculations　of99Tc　and129I　in　XAPR　were　done　by　ORIGEN2　code,　as　well　as　comparison　with　experimental　data,　the　difference　between　theoretical　and　experimental　data　mainly　comes　from　the　deviation　of　neutron　flux　used　and　the　actual　one.　Conclusions　were　made　that　XAPR　is　effective　in　transmutation　of99Tc　and129I.