Abstract: A new type of coils（fuor-coils group）aiming at creating more uniform magnetic field is designed, the thought of which comes from calculating the higher derivatives of the magnetic induction on the center line of Helmhohz coils. Showing from the images of the magnetic field,the amazing advantages of four-coils group against the traditional Hemhohz coils are able to be observed clearly.

Key words: uniform magnetic field, Helmholtz coils, four-coils group