In this work, the air drawing model and the air jet flow field model of the dual slot inset blunt die of polypropylene polymer nonwovens fabrics in melt blowing process were established. The effect of density and specific heat capacity of polymer melt at constant pressure changing with polymer temperature on fiber diameter are studied. The air jet flow field model was solved by using the finite difference method. The computational simulation results of the distributions of the z-components of air temperature and air velocity along the spinline during melt blowing process are in accordance with the experimental data. The air drawing model of melt blowing process was simulated by means of the numerical simulation results of the air jet flow field. The predicted fiber diameter agrees with the experimental data. The effects of processing parameters air initial velocity and air initial temperature on the fiber diameter. A higher air velocity and higher air temperature can yield the finer fibers. The results demonstrate that a higher air initial velocity and a higher air initial temperature are beneficial to the air drawing of the polymer melt and thus to reducing fiber diameter. The results show the great potential of this research for computer assisted design in melt blowing nonwoven process and technology. POLYM. ENG. SCI., 58:1817-1825, 2018. (c) 2017 Society of Plastics Engineers