In this paper, the radial resistivity variation (RRV) of the gas doped floating-zone (GDFZ) silicon has been studied through of three factors that are the lower shaft rotation speed, the timeratio of the lower shaft clockwise(CW) rotation speed and the counterclockwise (CCW) rotation speed, and the eccentricity between the upper shaft and the lower shaft in the horizontal direction. Test results show that the lower shaft speed has greatly influenced the RRV of GDFZ silicon, and with the increase of the shaft speed, radial deviation of the resistivity decreases first and then increases. As the timeratio between the lower shaft of CW&CCW rotation speed increases, the single crystal radial resistivity distribution is improved. As reversible angle of CW&CCW further increasing, radial deviation of the resistivity distribution rises again. With the increases in eccentricity ing, resistivity variation between the edge and the center decreases, thus radial resistivity inhomogeneity of single crystal significantly is also reduced. Based on the above study, further optimization of process, reasonable regulation and control of shaft speed, reversible angle, eccentricity and other parameters selected during GDFZ process can be obtained, which would obtain good radial resistivity uniformity to meet the requirements of the semiconductor devices.