Structure of the SnS ground state molecule is optimized by employing density functional theory (B3P86) method with 6-311++G** basis sets for S atom and SDB-cc-pVTZ for Sn atom. The effects of electric filed ranging from -0.04 to 0.04 a.u. are investigated on bond length, total energy, the highest occupied molecular orbital (HOMO) energy level, the lowest unoccupied molecular orbital (LUMO) energy level, energy gap, mulliken atomic charges, harmonic frequency and infrared intensity of SnS ground state molecule. The excited properties of SnS molecule under different electric fields are also studied by using time dependent density functional theory (TD-B3P86) method. The results show that the bond length and infrared intensity are proved to first decrease, then increase with the external field increasing, but the total energy, HOMO energy EH and harmonic frequency are found to first increase, then decrease. The LUMO energy EL and energy gap Eg are proved to decrease with positive direction electric field increasing. The transition wavelengths from the ground state to the first nine excited states increase with positive direction electric field increasing, but excited energies from the ground state to the first nine excited states decrease.