Four-quadrant detectors which consist of four well balanced detectors have been used for beam collimation and target tracking. In this article, we report a Stokes polarimeter based on a four-quadrant detector. By placing polarizers and wave plates in front of the individual detectors, the four detection channels were turned into four polarization analyzing channels of a Stokes polarimeter. An optimization algorithm was proposed to determine the axis directions of the individual polarizers, as well as the axis direction and the retardance of the wave plates for minimizing the errors and increasing the robustness of the measurements. The polarimeter is capable of simultaneous measurements of fast varying polarization states. Using properly selected polarization optics and following the same optimization algorithm, the polarimeter can be extended to other wavelength range, such as the infrared.