Slit pillar enables a small fraction of the mainstream flow through pillar to disturb the pillar wake zone fluid flow, and eventually enhance the local and global heat transfer performance in microchannels. In this study, three-dimensional full-domain numerical simulation analysis on the hydrodynamic and thermal performance of slit pillar array in microchannels with different slit angle pillars combination and different H/D ratios are investigated at Re=104~626. The comparisons are conducted on pressure drop, surface temperature, Nusselt number and thermal performance index. Furthermore, the results are analyzed using the entropy generation. As a result of the secondary flows and enhanced convective heat transfer area, results show all cases at H/D=0.3 demonstrate enhanced heat transfer performance with an increment of base Nusselt number by 18.0~34.7%, while a reduction of pressure drop by 3.4~12.9% simultaneously in comparison to the criterion case at the same conditions. Among them, slit15°-15° shows the best comprehensive heat transfer performance. Due to the improved uniformity of velocity and temperature distributions, all the slit pillar array microchannels show decreased entropy generation. The maximum entropy generation reduction can reach up to 15.8%, as compared with the criterion case at the same conditions. The above results fully demonstrates the novel slit pillar array microchannel heat sink as an effective approach for heat transfer enhancement.