By introducing sub-wavelength grating into an oxide-confined 980-nm vertical-cavity surface-emitting laser (VCSEL), the VCSEL with a stable polarization is realized. A sub-wavelength zero-order grating period is smaller than the wavelength in the semiconductor medium. This choice avoids a reduction in efficiency due to higher diffracting light. After the grating is etched, the threshold gains of E-fields parallel and perpendicular to the grating groves direction are different. The polarization therefore would be controlled. Good laser characteristics are obtained: the orthogonal polarization suppression ratio is over 12 dB and the threshold current increases just 7.14%.