The flow pattern of two-phase flow in micro-channels is a crucial issue in heat dissipation devices, as it significantly influences the heat transfer coefficient and pressure drop. Experimental investigations were carried out on nitrogen-water and nitrogen-ethanol flows within micro-channels. Pressure drop and flow patterns were measured using a pressure gauge and high-speed video system. As the nitrogen and liquid flow rates increased, slug flow, stirring flow, and annular flow sequentially appeared within the channels. Based on the measured pressure drop and observed flow patterns, an analysis was performed to establish the relationship between pressure drop and flow pattern. Numerical simulations of two-phase flows in inlet channels with sharp contractions were carried out using FLUENT solver to validate experimental results. Furthermore, discussions were held regarding the effects of fluid velocity and surface tension on convection patterns and pressure drops. Results indicate that both pressure drop magnitude and specific flow pattern are dependent on fluid velocity; specifically, increasing fluid velocity leads to slug flows transitioning into stirring flows followed by annular flows - consistent with experimental observations. Additionally, it was found that surface tension influences both separation location and length of slug bubbles.