The absorption efficiency of CO2 in the amine solvent system of the parallel-plate membrane contactor with countercurrent- flow operation was investigated theoretically and experimentally. A two-dimensional modeling equation for predicting the concentration distribution and total absorption rate was developed and the analytical solution for the resultant partial differential equations is obtained using the separated variables method with an orthogonal expansion technique. The theoretical predictions were presented graphically with the mass-transfer Graetz number and membrane location as parameters. The absorption efficiency, average Sherwood number and concentration distributions are represented graphically with absorbent flow rate, gas feed flow rate and inlet CO2 concentration in the gas feed as parameters.