Dispersion effect of the composite method (surface modification and electrostatic dispersion) on ultra fine powder in the air is studied. Van der Waals forces, liquid bridging forces and electrostatic forces of the inter-particles of composite dispersion are also discussed. The results show that the composite method can obviously improve powder dispersion. The improving of composite dispersion effect is attained through weakening van der Waals force and liquid bridging force by surface modification, and having particles charged with same charge by electrostatic technology.