Failure　behavior　of　brittle　materials　under　mixed-mode　loading　was　investigated　using　two　loading　forms:　(a)　Glass　sheet　specimen　with　an　inclined　crack　under　uniaxial　tension;　(b)　Uniaxial　tension　and　shearing　loads.　It　was　found　that　Mode　II　stress　intensity　factor　assists　crack　growth,　and　the　tensile　stress　parallel　to　the　crack,　y,　resists　crack　opening.　The　interaction　of　them　makes　little　contribution　to　crack　growth　due　to　the　neutralization　each　other　for　the　combined　load　KI　+K.II　+y,　whereas　KII　obviously　affects　the　fracture　in　the　mixed　load　KI　+KII,　especially　when　KII　/　KI　＞　1.　Experiments　showed　that,　under　complex　stress,　crack　propagate　always　along　the　direction　normal　to　the　maximum　strain.　Crack　growth　path　is　mainly　governed　by　Mode　I　stress　intensity,　but　the　critical　value　of　crack　driving　force　can　be　influenced　by　the　stresses　irrelevant　to　KI.　A　modified　equivalent　calculation　for　toughness　evaluation　for　inclined　crack　was　proposed.