Tandem pumping is characterized by high pump-source brightness and low quantum defect, which are beneficial for power scaling of fiber laser. By combining the modified chemical vapor deposition (MCVD) method with the chelate precursor doping technique, we fabricated an ytterbium (Yb)-doped aluminophosphosilicate fiber suitable for tandem pumping. Laser performances of the fiber were demonstrated in an all-fiberized master oscillator power amplifier (MOPA) laser system. Tandem pumped by 1018 nm fiber laser, 9.82 kW laser output at 1080.08 nm has been achieved with 86.8% slope efficiency. The 3-dB bandwidth is 1.62 nm at the maximum laser power. Our results indicate that the Yb-doped aluminophosphosilicate laser material is the optimal gain medium for the tandem pumping of high-power fiber laser systems. The chelate precursor doping technique combined with MCVD is an effective method for obtaining this type of material.