Temperature uniformity in a water-cooled mini-channel heat sink with different flow field configurations under high heating flux was numerically studied. A thermal resistance network model was established and the concept of variable-height channels was proposed to improve the temperature uniformity on the heating surface. The influence of flow field configurations on the flow distribution uniformity is firstly studied, and a circular turning constructal distributor was selected due to its best flow distribution uniformity and cooling performance. And then the effects of fluid velocity, heating area, substrate thickness and three novel channels on the temperature uniformity and thermal resistance were investigated. Result shows that for the heat sink with the circular turning distributor and variable-height channels, the temperature non-uniformity achieved on a 3 x 3 cm heating surface can be reduced to less than 1 K with the heat flux as high as 2 MW m(-2). (C) 2015 Elsevier Ltd. All rights reserved.