A multi-pass laminar counterflow mass exchange device is an open conduit divided into four subehannels with uniform wall concentration, by inserting three permeable barriers. Only the composition of the flow stream varies along the channels. The Sherwood numbers as well as the improvement of mass transfer efficiency have been investigated analytically by using an Eigenfunction power series expansion. The device performance results in multi-pass operations are represented graphically and compared with those in a single-pass device (without permeable barriers inserted). Analytical results show that there exists a best permeable-barrier position when both the mass transfer improvement and the increment of power consumption are considered and thus can effectively enhance the mass transfer efficiency compared with that of single-pass operations.