The flow boiling of liquid nitrogen in a micro-channel heat sink was experimentally studied for mass fluxes ranging from 62.6 to 598 kg/(m2·s). The heat sink was made of stainless steel. The experimental results showed that the heat transfer coefficient significantly increased with heat flux at low vapor quality where heat transfer was dominated by nucleate boiling. The heat transfer coefficient first increased with heat flux and then decreased with the increase in vapor quality after the heat transfer coefficient reached the peak value, which was due to flow pattern transition and the local dry-out. The experimental data was compared with the empirical correlations. Both results showed similar trend, but the calculated results were larger than the experimental ones.