To further expand the application range of microchannel boiling heat transfer in the field of high heat flux electronic equipment cooling, an experimental study is conducted on the dynamic characteristics of boiling generation and development, as well as the overall heat transfer characteristics of microchannel heat exchangers with parallel multiple channels. The results indicate that in microchannel heat exchangers with parallel multiple channels, there are significant differences in the initiation positions of boiling bubbles among the parallel microchannels. The deviation in the non-uniformity of the boiling inception position is relatively small under the influence of mass flow rate and decreases initially and then increases with the increase of heat flux density. Both subcooled boiling and saturated boiling heat transfer mechanisms occur simultaneously within the microchannels. Bubbly flow can happen in both boiling mechanisms, while slug flow and annular flow regimes only occur in the saturated boiling region. The heat flux density has a significant impact on the heat transfer mechanism within the channel, the wall temperature along the flow path, and its variation pattern. Within the heat flux density range of 63~80 kW/m2, the sudden expansion effect at the outlet plenum chamber cause the wall temperature at the heat exchanger's outlet reduce first, then increase, and then reduce again. As the heat flux density increases to 104~252 kW/m2, the wall temperature fluctuations in the microchannels are smaller, and temperature uniformity is enhanced. The overall boiling heat transfer characteristics of the heat exchanger show a turning point when the outlet refrigerant dryness at the microchannel exit is 0.02. The overall heat transfer coefficient of the heat exchanger increases with the increase of both mass flow rate and heat flux density, with the mass flow rate having a higher sensitivity to the average heat transfer coefficient.