Analysis of the single-cell concentration photovoltaic (CPV) system is challenging due to the high thermal stress across the solar cell surface area inducing extreme degradation of the electro-mechanical behavior. Although the good thermal performance shown by the passive cooling using heat sinks and the different optical configurations based on Cassegrain and Fresnel lens designs, the experimentally achieved concentration ratio (CR) is still below 5800 suns. The actively cooled heat sink integrating millimeter-scale pin-fin array inside a cooling channel can be promising toward minimum heat sink weight and maximum discharge of the generated heat. The current study presents a comprehensive analysis of a pin-fins cooling channel for a single-cell CPV system under ultra-high CRs. The thermal performance and the hydraulic resistance of five pin-fin heat-sink configurations were performed at different CRs and low Reynolds number for an Aluminum substrate material. The inline pin-fins heat sink (PFHS) displayed the minimum average cell temperature for all Reynolds numbers with thermal performance higher than its closest successor by 9.07%. The thermal performance and the pressure drop showed more dependence on streamwise spacing rather than spanwise spacing for all tested staggered pin-fin heat sinks. Pressure drop drastically increased at higher Reynolds number, Re = 726, for the inline pin-fin heat sink reaching a value of 288.20 Pa due to higher disturbance in the streamwise direction. The results demonstrate that the inline pins-fin heat sink with a constant distribution of circular axial grooves (plugs) along each pin can keep the solar cell within a safe operating temperature, that is, 80 degrees C, for CR up to 15 000 suns at an ambient temperature below or equal to 35 degrees C.