Abstract: According to requirements of physical parameters of undulator, we mainly design the size tolerance and structure of magnets and poles, the performance parameters of magnet and the measurement system of permanent magnet. The size tolerances of magnets and poles are 0.05 mm and 0.02 mm respectively along the beamline. The assembly and adjustment of magnets and poles are independent. At the same time, Helmhotz coils and magnetic field integral method are used to measure the magnet performance. Finally, the mechanical system and the gap adjustment system of the undulator are designed. It is found that the transom and bracket deformations are 1.5 m and 7.5 m respectively in the mechanical system. In the control system, clearance adjustment ranges from 18 mm to 32 mm, and adjustment precision and taper are 0.01 mm and 0.015 mm respectively.