The　convergence　of　the　tridiagonal　matrix　method　for　multicomponent　distillation　was　discussed　with　the　principle　of　numerical　analysis.　A　modified　method,　bidiagonal　matrix　method,　was　put　forward.　The　two　methods　were　compared　in　their　convergence　and　stability.　The　application　of　the　tridiagonal　and　bidiagonal　matrix　methods　to　the　calculations　of　many　non-ideal　multicomponent　distillations　demonstrates　that　the　latter　is　more　stable　than　the　former.