In the conventional microchannels, effective two-phase flow mixing and reverse flow inhibition are challenging for the enhancement of flow boiling performance. Although various researches have been extensively explored to improve flow boiling performance through functional structure geometries design and surface modification, sufficient two-phase mixing and successful reverse flow inhibition in the entire microchannel still lacks. In this study, a novel saw-like copper microchannel with high L/D (microchannel length relative to hydraulic diameter) is proposed and fabricated to enhance the fluid mixing and inhibit unwanted vapor backflow, corresponding flow boiling experiment is conducted to comprehensively investigate the thermos-hydrodynamic behaviors. The results indicate that flow boiling performance significantly improve owing to strong two-phase mixing and flow boiling stabilities in this new copper microchannel. At mass flux of 200 kgm^-2s^-1, the peak critical heat flux reaches 217 Wcm^-2 and heat transfer coefficient is up to 110 kWm^-2K^-1, respectively. Compared with conventional plain microchannel, critical heat flux and heat transfer coefficient are increased by 51 - 85 % and 70.0 − 110.0 % in the present design. Additionally, the heat transfer performance in the forward direction outperforms that in the backward direction, which demonstrated the importance of two-phase stabilities.