The three dimensional laminar flow structures and forced convective heat transfer of shear-thinning power-law fluids in dimpled and protruded microchannel were investigated in this study. The CMC (Carboxyl Methyl Cellulose) aqueous solutions with various concentrations were employed as the working substances. The dimples and protrusions with relative depth delta/D of 0.1, 0.2 and 03 were vertically aligned to arrange on the opposite walls. The results reveal that the modes of separation flow near protruded walls, observed at some cases with delta/D = 0.2 and 0.3, obviously differ from that near dimpled walls. Both the scale and intensity of all the separation bubbles are strengthened with the increase of flow rate and CMC concentration, except 4000 ppm. While, the results at cases of 4000 ppm show the variable geometrical structure of protrusion can overcome the negative effect of large CMC concentration on heat and mass transfer. Moreover, the heat and mass transfer of main flow and near-wall flow, as well as the strengthened secondary flow in the passage, are enhanced by the dynamic viscosity distinction of working substance, differing from the Newtonian flow. Furthermore, relative Fanning friction factor f/f(0) increases with the increase of depth of dimple/protrusion and flow rate and the decrease of CMC concentration. Relative Nusselt number Nu/Nu(0) continuously increases with the increase of flow rate and depth of dimple/protrusion. And then the maximum and minimum thermal performance TP are observed at the case 2000 ppm with delta/D = 0.3 and CMC100 with delta/D = 0.1, respectively. At last, new correlations of f/f(0) and Nu/Nu(0) are proposed based on the results in this study with a well-established data fitting. (C) 2016 Elsevier Ltd. All rights reserved.