Abstract: The study of condensation for high-speed expansion gas is still on the stage of exploration, and the popular nucleation model may be Internally Consistent Classical Theory(ICCT). However, satisfied results can be gained for real-gas in low temperature. As far as theory's defects, the model is modified as follows: computing chemical potential difference with fugacity and using Tolman model to solve the relation between droplet curves and surface tension; SRK and LD formula were recommended respectively for state equation and surface tension in low temperature. Compared the modified model and ICCT model with the experiment data, it is found that ICCT predictive value is higher than experiment value about 3-4 order of magnitude while deviation of modified model can be reduced to 1-2 order of magnitude, especially for alkane the deviation under 1 order of magnitude. For modified model, more satisfied results can be gained, it can be recommended as standard formula for the study of nucleation.