Software　aging　related　failures　can　be　prevented　by　applying　software　rejuvenation　technology.　But　the　restart　operation　in　the　software　rejuvenation　phase　makes　the　system　unable　to　provide　services,　which　leads　to　system　unavailability.　The　software　rejuvenation　model　with　pre-start　technology　is　therefore　proposed　to　reduce　downtime　and　improve　availability　by　switching　between　active　copy　and　backup　copy,　which　can　substitute　for　restart　operation　and　resolve　unavailability　problem.　First　of　all,　the　rejuvenation　operation　of　model　with　pre-start　technology　is　described　and　improvements　on　the　conventional　model　are　presented　Second,　the　model　availability　is　calculated　by　Markov　Regenerative　process.　And　finally,　according　to　the　experimental　results,　current　model　proves　to　be　more　available　than　the　conventional　one.