Abstract: To study the space variation of longitudinal piezoelectric constant and electromechanical fator of 32 and 3 m crystals of trigonal system, the method of studing macroscopic tensor space distribution is introduced. Longitudinal piezoelectric properties in space of the two kinds of crystals are discussed respectively. The results show that, for 32 crystals, the absolute values of the longitudinal piezoelectric constant d₁₁^' and electromechanical factor k₁₁^' distribute in space in the shape of 6 petals, and maximum values of d₁₁^' and k₁₁^' are equal to that of d₁₁ and k₁₁ which are along the x-axis; for 3 m crystals, the longitudinal piezoelectric constant d₃₃^' and electromechanical factor k₃₃^' exist the maximum values in special orientation, and along these corresponding directions which depend on the crystals, the longitudinal piezoelectric properties can be greatly enhanced.