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　epsilon(33)　and　piezoelectric　d(33)　exhibit　the　same　trend　with　the　calculated　ones　in　YOZ　plane.　Their　longitudinal　piezoelectric　coefficient　d(33)　can　be　enhanced　greatly　near　60　degrees　direction　canted　away　from　the　[111]　rhombohedral　direction.　The　enhancement　of　longitudinal　piezoelectric　coefficient　d(33)　along　a　nonpolar　direction　can　be　understood　as　a　consequence　of　the　large　shear　piezoelectric　coefficients.