The possibility of describing the jet from the dual slot die in the melt blowing process with a vortex pair was studied according to the nature of the vortex. A model of the synthesis of two jets was developed, The reliability of the model was confirmed by experimental data cited from literature. The prediction of the fiber diameter using this model coincided with that using the fitted equation with the data advanced by Harpham and Shambaugh. The effects of the equipment parameters, such as the angle between the air flow and the axis of the spinneret, the width of the die head and the width of the slot were also discussed.