The　dielectric　and　piezoelectric　coefficients　of　lithium　niobate　(LiNbO3)　and　lithium　tantalite　(LiTaO3)　single　crystals　have　been　theoretically　calculated　and　experimentally　measured　for　different　cutting　orientation　directions.　For　LiNbO3　and　LiTaO3,　the　measured　effective　dielectric　Ε33　and　piezoelectric　d　33exhibit　the　same　trend　with　the　calculated　ones　in　YOZ　plane.　Their　longitudinal　piezoelectric　coefficient　d33　can　be　enhanced　greatly　near　60°　direction　canted　away　from　the　[111]　rhombohedral　direction.　The　enhancement　of　longitudinal　piezoelectric　coefficient　d33　along　a　nonpolar　direction　can　be　understood　as　a　consequence　of　the　large　shear　piezoelectric　coefficients.