A class of approximate interpolation formula for the partition function of the 3-dimensional Ising model is proposed on the basis of a previous analysis of the 2-dim rigorous solution and 3-dim Q-approximation. In principle, the present knowledge about the location of the singular point and the low- and high-temperature expansion coefficients can be incorporated provided a sufficient amount of computation is carried out. One and the same analytical expression leads to good low- and high-temperature behaviour except for the specific heat singularity.