When using vertical-cavity surface-emitting lasers (VCSEL) as laser source, in order to obtain high-power polarized laser, polarization feature 980 nm large-aperture bottom-emitting VCSEL is investigated in this paper. A rectangular-shaped VCSEL is fabricated by etching rectangular mesa structure and rectangular output aperture. The maximum power of bottom-emitting rectangular-shaped VCSEL is 660 mW with 550 μm×300 μm output aperture under continuous wave condition, and the differential resistance is 0.09 Ω. It is found that H-polarization (horizontal) and V-polarization (vertical) demonstrated steadily coexistence over the entire range of operation current. And H-polarization dominated over V-polarization which is parallel to the shorter side of the rectangular output aperture. Compared with the circular-shaped VCSEL, both H-polarization and V-polarization nearly have the same lasing situation. Spectrum blue-shift of H-polarization light occurres with respect to V-polarization light. This phenomenon is explained by the symmetric three layer waveguide model. The dependence of the orthogonal polarization ratio on the aspect ratio of the output aperture is investigated in the rectangular-shaped VCSEL. It is found that the rectangular post is an effective way to stabilize the output polarization of large-aperture VCSEL, which can emit high-power polarized laser.