The present study is mainly aiming at numerically analyzing the combustion and emission characteristics of the diesel spray in a high-pressure environment. Computations are peformed for the peak chamber pressure with range from 4.08 MPa to 162 MPa. Numerical results indicate that the pressure increase in combustion chamber significantly influences the mechanism for droplet dynamics and mixing characteristics, spray penetration autoignition, flame lift-on height and the propagation or fuel vapor and flame. By increasing the ratio or the ambient density to injected liquid density, the fuel-air mixing rates and the burning rates increase and the $NO_x/soot$ emission level decreases.