Membrane distillation (MD) is a separation process which higher vapor pressure components are evaporated in mixed liquid solution through hydrophobic membrane with 0.1 or $0.5{mu}m$ pore size. In this study, direct contact membrane distillation process for hollow fiber module were interpreted numerically using the "COMSOL Multiphysics" software. The variables for the system were temperatures and flow rates of lumen and shell side solutions. The permeate flux increased from 1.0 to $3.8L/m^2{cdot}hr$ as temperature of the feed solution for lumen increased from 30 to $50^{circ}C$. However the effect of shell solution temperature on permeate flux was relatively low. Also, the optimum velocity of lumen feed was obtained at 0.15 m/s ($Re_L=135$) by considering MD permeate flux as well as operating pressure loss.