Abstract: The maghetic field of Helmholtz coils and the theoretical calculation results on its uniform degree show that when the constant electric currnt is througt the coils, a constant uniform magnetic field Bo is formed at the center of the coil. At x=y=0.2, the maximum of(Bx~Bo)/Bo is 0.30% and that of By/Bo is 0.16%. According to the abovementioned calculated results and the appeacance dimension of the ceramic declination magnetic variometer, the scale value meter is designed and edveloped, which matches the declination magnetic variometer, This paper discusses the design train of though for the scale value meter and its theoretical base and also introduces the structure, technical Parameters of the scale value meter and the method for its usage.