Based on the measurement results of air flotation sewing machine needle bar and surface form changes, a numerical model close to the real case surface of needle bar was established, and the dynamic control equation of air flotation sewing machine needle bar was deduced. The dynamic change principle of the data model for needle bar reciprocating motion was analyzed, solves the air flotation sewing machine needle bar dynamic control equation using the finite difference method. Compared simulated performance between the ideal needle bar and the one with form error. The results show that: the surface of the needle bar with form error can be produced relatively obvious dynamic pressure effect in dynamic situations, provided a larger capacity gas film.