The problem of free-form object modelling in CAGD is an actual task in computer graphics and solving it is important for practical use. This paper describes a new approach of semi-numerical computing volume of solids bounded by rational Bézier surface set. There is an approach for volume calculation of solids bounded by simple Bézier surface set. In this paper, the proposed approach is based on the combination of analytical integration for volume integral computation and numerical integration for rational function integral computation.