A wetting mechanism was presented for the system of hydrophobic hollow fiber membrane-alkanolamine absorbents for CO 2 capture. A mathematical model was developed by means of correlating the resistance-in-series equation, the Laplace equation and the pore size distribution function of membrane based on the wetting mechanism. Effects of operation pressure, membrane configuration and operation temperature on membrane pore wetting were investigated experimentally and theoretically. Both experimental and model results show that, the wetting of membrane pores significantly affected the mass transfer coefficients of the membrane module, and resulted in the mass transfer stability of membrane phase and operation performance declining rapidly. Aqueous organic solutions easier wetted the hydrophobic membrane pores than water. The effects of membrane with high porosity for pore wetting on mass transfer are significantly greater than that of membrane with low porosity, and the performances of mass transfer of the higher porosity modules would deteriorate more easily. Liquid side operation pressures in the module significantly influence the pore wetting and the resistance to mass transfer of membrane phase. The overall mass transfer coefficients decreased rapidly with the increase of the liquid side operation pressures. The parameter of temperature is a sensitive factor for pore wetting of hydrophobic membrane. The wetting mechanism was validated experimentally and the model was in agreement with experiments.