The sensitivity of multi-collector inductively coupled plasma mass spectrometers (MC-ICP-MS) can be significantly improved using different sample and skimmer cones with different orifice diameters and angles. In this study, an MC-ICP-MS with three typical combinations of sample and skimmer cones [(H skimmer cone + standard sample cone (Standard + H), X skimmer cone + standard sample cone (Standard +X) and X skimmer cone + Jet sample cone (Jet +X)] was used to measure the boron isotopes, and the effect of the different combinations of sample and skimmer cones on the sensitivity of the MC-ICPMS and the underlying physical principles were investigated. The results suggest that more ions can be introduced into sample cones with larger orifices, which results in increased sensitivity. Compared with standard skimmer cones (which have cylindrical entrances and trumpet-shaped exits), X skimmer cones (which have trumpet-shaped entrances and exits) can provide more space for ion beams to entrance the skimmer’s orifice after they are subjected to the space-charge effect.