The aim of this work is to investigate the combustion dynamics of ethylene/air flames at atmospheric pressure in a micro-flow reactor over a wide range of equivalence ratios (0.3<φ<1.5). The presence of three main flame regimes was confirmed: stable flames, Flames with Repetitive Extinction and Ignition (FREI) and weak flames. Weak flames were observed at equivalence ratio of 0.3, confirming the potential of micro-combustor technology under ultra-lean conditions. Furthermore, the stable flames analysis allows us to find a correlation between the stabilization temperatures of these flames and the laminar flame speeds at various equivalence ratios. Regarding the unstable flames, it was possible for the first time to follow the flame progression at high frequency using a high-speed camera and the results were compared with the CH* emission profiles obtained with an EMCCD camera. Finally, the existence of oscillating flames between the three main flame regimes was confirmed, and a frequency analysis was performed.