The crystalline structure of Zn2(OH)PO4 (ZPOH) belongs to orthorhombic unit cell structure, space group of P21212, which has no center of symmetry. Based on the plane-wave pseudopotential ab initio method, the electronic structure, linear refractive indices and second harmonic generation (SHG) coefficients of Zn2(OH)PO4 were calculated and the Sellmeier equations were also fitted. To verify the calculated values, ZPOH was synthesized using hydrothermal method, and the measured SHG effect is in accordance with the theoretical calculation. The ultraviolet (UV) cut-off edge and thermal stability of ZPOH were also reported for the first time.