Doping bismuth ions in the lattice of ceria was found to be an effective method for improvement of the catalytic performance. Herein, a series of CexBi1-xOy (x = 0, 0.25, 0.5, and 0.75) catalysts was synthesized by the reverse coprecipitation method, and their catalytic activities were evaluated at both loose and tight contact modes. It was found that doping of Bi in the CeO2 lattice significantly improved the mobility of lattice oxygen in CexBi1-xOy catalysts, and Ce0.5Bi0.5Oy demonstrated the best catalytic performance, especially at loose contact mode. The activation energy of soot combustion for Ce0.5Bi0.5Oy was determined to be 133 kJ mol(-1). The impact of Bi doping on the low-temperature activity of CexBi1-xOy catalysts was also examined. It was found that the lattice oxygen of unstable Bi-O-Ce species was easier to transfer to the catalyst surface and react with soot at high temperatures. The cyclic tests of catalysts demonstrated that Ce0.5Bi0.5Oy could maintain a decent thermal stability. Overall, this study discovered the importance of lattice oxygen in soot combustion for the doped catalysts, which is of great significance for their future applications.