Ultracold molecules have wonderfully potential applications in quantum system, precision measurement, and chemical dynamics, and so on. Thus, people have a strong desire for investigating the potential cooling candidates. Feasibility of laser cooled OH molecules is investigated by ab initio quantum chemistry. Potential energy curves for the ground state X2Π and low-lying excited state A2Σ+ of OH molecules are calculated by multi-reference configuration interaction method to develop an applicable cooling transition. In order to obtain more accurate results, the calculations involve Davidson corrections, scalar relativistic corrections, core-valence correlation, and spin-orbit coupling effects. Based on the obtained potential energy curves of Λ-S and Ω states, spectroscopic parameters are determined by solving the one-dimensional radial Schrödinger equation, which are in good agreement with available theoretical and experimental values. The permanent dipole moments, transition dipole moments, vibrational levels, Franck-Condon factors and radiative lifetimes of OH molecules are also calculated. The results indicate that the OH molecule has a highly diagonally distributed Franck-Condon factor (f_{00}=0.9053) for the A2Σ+ (ν'=0} ight) → X2Π (ν"=0} ight) transition and short radiative lifetime (τ00=5.8363×10-7 s) for the A2Σ+ state. It means that the OH molecule meets the criteria as a promising candidate for direct laser cooling, which can ensure rapid and efficient laser cooling. Finally, a specific scheme for laser cooling of OH molecules is proposed, and the scheme for the A2Σ+ → X2Π transition requires three laser wavelengths, i.e., main pump laser with λ00=307.1532 nm, two repumping lasers, with λ10=344.9163 nm and λ21=349.7659 nm, respectively. The data imply the probability of laser cooling OH molecules with three electronic levels. In addition, the calculated results also indicate that spin-orbit splitting of X2Π is much less than vibrational level, which leads to the conclusion that spin-orbit coupling has no effect on laser cooling scheme of OH molecules. The results above will provide an important theoretical basis for preparing ultracold OH molecule.