Abstract: Numerical simulation was employed to study the uniformity of velocity field and temperature field in parallel mini-channel heat sink. Effect of interior spatial structure and flow rate on heat transfer characteristics of mini-channels heat sink were explored. Result showed that, the mini-channel heat sink with diagonal single inlet and single outlet present low flow rate in middle and high flow rate in two sides of parallel mini-channels. And the phenomenon of non-uniformity was apparent with increasing of flow rate. The uniformity of mini-channels flow rate was improved by setting up guiding component in inlet and outlet region. However, the improvement effect was inconspicuous with increasing flow rate. Mini-channels heat sink with mini-channels derangement has the better flow distribution coefficient. Therefore, pressure drop and mean temperature of heat surface were considered, and mini-channels heat sink with mini-channels derangement presents better performance.