To improve the efficiency and yield of Mini/Micro LED mass transfer and self-assembly， a new positioning magnetic needle using a permanent magnet + electromagnetic magnetic field coupling is proposed. An electromagnetic bias coil is designed to precisely control the magnetic force on the needle's upper surface for accurate chip grasping. Magnetic circuit analysis establishes a mathematical model for the magnetic needle structure， identifying parameters affecting the magnetic flux density in the air gap. The finite element method optimizes these parameters， increasing the Bmax on the needle's upper surface from 57 mT to 68 mT， a 19.2% improvement， and enhancing the peak-to-valley variation rate δ from 50.8% to 70.5%. Based on these optimizations， a permanent magnet bias positioning magnetic needle device was developed. Tests show the optimized needle achieves a B_max of 60 mT and a δ of 66.6%， efficiently securing thousands of chips per minute. This meets precise chip grasping requirements and enhances the yield of self-assembly mass transfer technology when combined with fluid.