A method for lower power consumption of planar coil fluxgate, which based on the standpoint of demagnetizing field, and according to this method to optimize coil and core structure of fluxgate and simulation verification. Planar coil fluxgate possesses the advantages of simple structure and preparation, but its large power consumption needs further research which caused by poor coil exciting efficiency and large excitation coil resistance. This paper on the basis of the analysis of planar coil fluxgate theory, present the way to reduce the power consumption of the fluxgate sensor which using the standpoint of demagnetizing field, and based on this method to design several planar coil fluxgate structure, finally make magnetic field simulation, and the simulation results provide theoretical support for further devices preparation.