Evaluation　of　rock　mass　quality　is　a　complex　system　problem　with　uncertainty.　For　the　sake　of　accurate　evaluation　of　the　estate　of　rock　mass　quality,　and　to　provide　scientific　basis　for　the　prevention　of　rock　mass　quality,　the　evaluating　method　for　rock　mass　quality　based　on　fractal　interpolation　theory　was　brought　forward.　Firstly,　eight　key　factors　were　chosen　to　construct　the　model.　In　addition,　because　of　few　standard　samples,　fifty　standard　samples　were　produced　by　the　way　of　stochastic　interpolation　on　basis　of　classification　standard.　Secondly,　through　calculating　the　fractal　dimension　of　single　index　of　rock　mass　quality,　the　fractal　dimension　exponent　evaluation　of　the　index　of　single　rock　mass　quality　with　the　maximum　likelihood　classification　principle　was　confirmed.　Thirdly,　adopting　weighted　summation　value　this　method　calculated　the　level　of　the　colligate　estimation　of　multi-index　of　rock　mass　quality　and　established　the　fractal　interpolation　evaluation　model　according　to　the　relationship　between　the　value　of　comprehensive　evaluation　of　the　samples　and　the　experience　level.　Finally,　four　samples　were　classified　based　on　the　model.　The　classification　results　are　consistent　with　that　from　other　methods.　It　is　shown　that　the　model　here　is　feasible　and　effective　in　evaluating　rock　mass　quality.　Moreover,　particular　score　of　each　sample　can　be　computed　by　the　model,　and　so　it　has　more　precise　classification　and　is　a　better　new　method.