A membrane distillation (MD) process with brine circulated in the cold side was developed. This process combines the ordinary MD with the osmotic distillation (OD), and is therefore called membrane osmotic distillation (MOD). The effects of brine concentration, liquid temperature, temperature difference between the warm and cold sides and liquid flow rate on water flux and heat efficiency of the process were investigated. Comparisons of MOD with MD and OD were carried out. It was found that MOD has the advantage of achieving higher water flux and heat efficiency simultaneously. A relation of the MOD water flux to the MD and OD water fluxes was given.