In this paper, the improvements of a kilogram level inertial mass measurement experiment in the National Institute of Metrology (NIM) are introduced. The systematic effect due to the mechanical deformation of the balance beam is reduced by adopting a new designed beam in conjunction with a mass center compensation idea. A new capacitor system, which can generate plus elastic force, is used to replace the previous Kelvin capacitor system to fasten the oscillation, and hence the measurement repeatability of oscillation periods can be improved. The Planck constant h is expected to be measured with a higher accuracy.