In order to explore flow characteristics of nonNewtonian fluid in bifurcation microchannel,the nonNewtonian fluid power law model was introduced into Newtonian fluid lattice Boltzmann model,and the flow behaviors of shear thinning fluid with different mass fraction were numerically simulated in rectangular crosssection microchannels with different bifurcation angles.The pressure distribution in the microchannel and the pressure drop in the flow region were obtained by analyzing the change trend of density with time in the flow process and the density under steady flow.The effects of solution mass fraction,inlet velocity and bifurcation angle on the flow characteristics of non-Newtonian fluid were analyzed,and the influence mechanism of fluid characteristics and micro channel geometry on the flow behavior of nonNewtonian fluid was discussed.The results show that the pressure drop of fluid in microchannel with 90° bifurcation angle is the smallest.The pressure drop is decreased with the increasing of bifurcation angle when the bifurcation angle is greater than 90°.However,the pressure drop is increased with the increasing of bifurcation angle when the bifurcation angle is less than 90°.The higher solution concentration makes the influence of the bifurcation angle and the inlet velocity on the pressure drop at the outlet more significant.The pressure drop at each section in the microchannel is parabolic