CdS nanocrystal is especially investigated by first-principles calculations and experi-ment. Based on phonon spectra, the wurtzite CdS structure is thermodynamically stable. Debye temperature, specific heat capacity and thermal expansion coefficient are calculated to be 221.51 K, 47.68 J.mol^-1K^-1 and 1.95x10^-4 K^-1 , respectively. Band gaps of CdS single crystal and monolayer CdS supercell calculated by GGA–mBJ function are 2.74 eV and 2.38 eV. CdS powder is synthesized by microwave-hydrothermal process (140 ^oC + 15 min), with particle size ranging from 50 to 1000 nm. HRTEM shows the nanocrystal distance of 6.676 Å between the (0001) crystal faces and growth preference along the [002] direction. The band gap of CdS thin film evaluated by UV–Vis absorption spectra is 2.41 eV, close to 2.38 eV of monolayer supercell, which provides theoretical basis for CdS doping to improve photoanode performance of piezoelectric semiconductors.