Based on Sachs scaling, an engineering computational model on air blast wave at high altitudes is presented in this paper. The model is built on analysis from numerical simulated pressure time data of shock wave in air. The model describes the peak overpressure, impulse, and typical time of the shock wave with new parameters. Comparison of pressure, density and velocity configuration for the different altitudes shows that the present engineering model can give consistent results with the numerical code. At last the scaled peak overpressure and the scaled impulse figure for the different altitudes are given for convenience of engineering application.