All piezoelectric coefficients and electro-optic coefficients of Zn(SCN)2·2H2 crystal have been measured by interferometry for the first time and results obtained are d14 =-8.8, d25=-15.8, d36= 1.2(×10-12C/N); γ41=4.5, γ52 =6.4, γ63= 0.8(×10-12m/V).