A　conductance　blockade　effect　has　been　observed　in　the　magnetic　tunnel　junction　consisting　of　La0.7Sr0.3MnO3　electrodes　and　a　SrTiO3　barrier.　The　blockade　effect　is　correlated　with　the　space-charge　trap　states　in　the　barrier.　The　blockade　threshold　eV(B)=128　meV　is　significantly　greater　than　Coulomb　charging　energy　E-C=11　meV.　The　blockade　can　be　lifted　with　a　magnetic　field,　accompanied　by　a　very　large　magnetoresistance　up　to　10　000%.　The　intriging　blockade　behavior　is　distinctly　different　from　the　conventional　Coulomb　blockade　effect,　showing　a　unique　spin-dependent　tunneling　process　mediated　by　the　localized　charge　trap　states.