To research the beam quality of high power vertical cavity surface emitting lasers (VCSELs) singledevices,the impact of the factors such as the current, the aperture, the substrate thickness on the M2 factor, the far field divergence angle, near field and far field intensity distributionsis analyzed. It'sconcluded that, the current density of active area tends to be uniform with the increasing current until the current gets crowded, which inducesall partsemitting and has a circular symmetric beam distribution.The beam quality factor will be smaller with the improved beam quality. On the other hand, with the increasing aperture size of the active region, the lasing intensitydistribution becomes more uneven. While, beam quality will be worse with the increasing aperture size.For the effect of substrate thickness on the beam quality, all the factorsare considered, the optimum substrate thickness is about 100 μm. In order to obtain high power and high beam quality for the VCSELs single device, the oxidation diameter of 650 μm and P side electrode diameter of 580 μm are chosen, which can realize the uniform distribution of current density in the active region and the effective limits on current. This study provides a basis for looking for an effective method to improve the beam quality.