In this paper, the influence of the addition of n-butanol on fuel properties, combustion, and emission characteristics for a diesel engine was studied. Kinematic viscosity, lower heating value, closed-cup flash point, density, cetane number, and distillation were measured. The engine performance and emissions were also tested at nine loads of 1200?rpm. On this basis, numerical models of the diesel at 100% load for five fuels were established based on Computational Fluid Dynamics (CFD). Next, CFD was used to evaluate the interactive influences among fuel properties and emissions quantitatively. The results demonstrated that kinematic viscosity, lower heating value, closed-cup flash point, density, and cetane number presented downward trends of varying degree with the increase in n-butanol content. Also, 10?vol.?%, 50?vol.?%, 90?vol.?%, and 95?vol.?% distillation temperatures decreased, and the range of decline decreased gradually. Hydrocarbon (HC), carbon monoxide (CO), and particulate matter emissions decreased, while nitrogen oxides (NO x ) emissions and fuel consumption increased. In the combustion process, the regions of concentration for the formation of HC and CO were the gap and near the wall, and the production of HC emissions lagged behind that of CO emissions.