This study proposed a Y-type mixer which was driven by electroosmotic flow (Ex = 5 - 25 kV/m) with 7 different mixing angles (30¢X, 60¢X, 90¢X, 120¢X, -120¢X, -90¢X, -60¢X) to enhance mixing efficiency . The mixing performance of the device was demonstrated by using micro laser-induced fluorescence (£gLIF) technology to quantify the concentration distribution in the microchannel. Also, micro particle image velocimetry (£gPIV) was used for velocity measurements and analysis. It was found that the negative mixing angle could induce larger dead zone area than the positive one. The joule heating effect was found when electric field strength was larger than 15 kV/m. The combined dead zone and joule heating effect could enhance the mixing performance slightly. Although it has only a marginal effect on the mixing length for the positive mixing angles. Negative mixing angles allow a reduction of mixer size, which means a more efficient use of material and space. Finally, the best mixing angle was found to be -60¢X.