Numerical simulation was made of two-fluid mixing in a microchannel. Since two fluids with different properties come into the microchannel, solute concentration is a key parameter of the two-fluid mixing in a microchannel. Glycerol solution with water was chosen as a working fluid, where the viscosity, density and diffusivity are a function of solute concentration. The governing equations of continuity, 3-dimensional momentum and solute species were solved numerically. A simple Y-channel was employed as a test microchannel. To validate the numerical simulation, measurements of velocity profiles were performed by μPIV(micro particle image velocimetry). Toward this end, a micro Y-channel was fabricated. Two advanced algorithms were applied, which are iterative multi-grid algorithm and CBC(correlation based correlation)based on FFT algorithm. Four cases with two different inlet concentrations were used to see the effect of concentration on mixing and the occupation rate of two fluids using two criteria of mixing; one is the mixing uniformity, the other is the mixing area.