In the case study of GRAPES_GFS, the vertical velocity on the upper level over the Antarctic continent has big computational noise, affecting the integral stability, and even causing the integral interruption. The diagnostic analysis of its dynamical core and physics-dynamics couple scheme indicates that the vertical interpolation of the potential temperature at the Lagrangian departure points is the main source of noise. Monthly case study of July 2013 shows that by introducing the vertical non-interpolated Lagrangian scheme into the thermal equation, this computational noise can be greatly reduced or eliminated. The comprehensive performance in the Northern Hemisphere and tropical region has improved significantly, and the serious loss of mass in 8 d integration process has been significantly alleviated.