Abstract: Volume of fluid（VOF） model and user-defined function were applied to simulate the flow boiling of water in microchannel with V-shaped, trapezoidal, square and dovetail-shaped cavities on the heating wall. The effects of cavity shape on the bubble behaviors of bubble nucleation, growth, detachment and coalescence were analyzed. The results show that when the heat flux on the wall is 300 kW· m^-2, all cavities are activated as boiling nucleation sites. Compared with the other cavities with V, trapezoidal and square shapes, the onset of boiling time in microchannel with dovetailed cavities is relatively earlier when flow boiling occurs. In the nucleate boiling stage, compared with the trapezoidal cavity, the growth and detachment times of the bubble in the microchannel with dovetailed cavity are decreased by 7.50 ms and 6.70 ms, respectively, while the detachment frequency of the bubble is increased from 33.8 s^-1 to 66.7 s^-1, which is helpful to enhance the flow boiling heat transfer of water in microchannel. The coalescence and elongation of the detached bubbles in microchannel can increase the evaporation area of liquid film near the heating wall and improve the disturbance of the liquid phase simultaneously. However, it can cause local drying on the heating wall and reduce the stability and reliability of flow boiling heat transfer in microchannel.