A phenomenological soot model of acetone-butanol-ethanol (ABE) was proposed with modification of the fuel pyrolysis process, and the oxidation effect on soot number density was also included. Using KIVA-3 V Release 2 code coupled with this ABE soot model, multi-dimensional computational fluid dynamics (CFD) simulations of ABE spray combustion in a constant volume chamber were conducted to investigate the effects of ambient oxygen concentrations on combustion and soot emission characteristics. Validation experiments were also conducted in an optical constant volume combustion chamber under 1000 K initial temperature with varying oxygen concentrations (21, 16, and 11%). The results demonstrated that predicted time-related soot mass showed good agreement with experimental data qualitatively. The total yield of soot mass initially increased with decreasing oxygen concentrations from 21 to 16% and then decreased to the lowest level at 11% ambient oxygen. The non-monotonic ABE soot behavior with a decreasing ambient oxygen concentration was related to the transition of the dominant effect from the suppressed soot oxidation mechanism to the suppressed formation mechanism.