Abstract: In this paper, the mass transfer problem of laminar natural convection for non-newtonian power-law fluids was studied. Several differential equations had to be solved for this purpose. The power-law model was adopted as an constitutive equation. An asymptotic solution, represented in dimen-sionless form by the relation among Sherwood number Sh and power-law Grashof number Gr and power-law Schmidt number Sc was given: Under the special condition(n = l), the asymptotic solution turned out to be similar to that for Newtonian fluids. Experiments were carried out with an electrochemical method. CuSO4-H2SO4-PAM(polyacrylamide) system under natural convection at vertical electrodes was studied through the current/voltage curve, which gave the limiting current and the mass transfer rate. A comparison betwene theoriti-cal results and electrochemical experiment data was made, it was found that, apparently asymptotic solutions conformed very well with electrochemical experimental data.