Based　on　a　visco-elastoplastic　model　considering　the　feature　of　water　degradation　effect　of　rock,　its　finite　difference　scheme　is　presented.　Through　program　development　for　the　model　by　C++　language,　the　FLAC3D　dynamic　link　library　file　is　obtained.　To　test　the　model　effectiveness,　it　is　shown　that　the　model　program　can　better　simulate　the　instantaneous　elastic　deformation,　attenuation　creep,　creep　constant,　water　degradation　and　plastic　deformation　characteristics　of　rock.　With　the　numerical　calculation　for　an　on-site　tunnel　geological　model　by　the　visco-elastoplastic　model　program,　it　is　shown　that　the　vault　settlement,　convergence　and　uplift　deformation　increase　with　the　growth　of　moisture　content,　and　the　time　that　surrounding　rock　remains　stable　is　shortened.　Uplift　displacement　in　saturated　state　is　twice　of　that　in　natural　moisture　state;　and　the　time　that　surrounding　rock　remains　stable　in　saturated　state　is　less　than　that　in　natural　moisture　state　for　about　40　days;　so　reasonable　construction　time　for　the　second　supporting　is　also　greatly　shortened.　The　calculation　results　are　consistent　with　the　measuring　results　in　the　tunnel　site,　which　can　explain　the　generation　mechanism　of　large　deformation　disaster　effectively.　Both　stability　of　rock-support　system　and　reasonable　time　for　the　second　supporting　can　be　well　predicted　by　the　visco-elastoplastic　model　program　presented　above.