To study the soot precursor emission characteristics of a n-butanoldiesel blend during low-temperature combustion (LTC), a model of n-heptane, n-butanol, polycyclic aromatic hydrocarbons (PAHs), and toluene was chosen. Computational fluid dynamics (CFD) software was used to establish a three-dimenisonal (3D) numerical model and to couple it with the chemical kinetics mechanism. The factors studied on soot precursor production were n-butanol blending ratio, exhaust gas recirculation (EGR) rate, injection timing, and intake pressure. The results showed that the formation of four types of soot precursors benzene (A(1)), naphthalene (A(2)), phenanthrene (A(3)), and pyrene (A(4) was delayed and the final amount of precursor produced decreased with increasing the n-butanol blending ratio. The delay in formation of these precursors and the reactions mostly occurred during the premixed combustion stage and with increasing the EGR rate. The final amount of A(1) produced increased with the EGR rate; however, those of A(2), A(3), and A(4) showed a decreasing trend after an initial increase, and the EGR rate corresponding to the peak decreased with increasing the n-butanol blend ratio. The final amounts of A(2), A(3), and A(4) produced increased with increasing the intake pressure. Soot precursors A(1), A(2), A(3), and A(4) formed in advance during the injection timing advancing with the final amounts of A(1) and A(3) produced were less. The final amounts of A(2), and A(4) produced showed a decreasing trend after an initial increase.