The invention provides a preset 'High Vacuum Densification' soft foundation process method, used for the soft foundation process requiring backfill. The method provided by the invention comprises presetting a drainage equipment required by 'High Vacuum Densification' on the original terrace in the construction area before backfill. By adopting the method provided by the invention, the risk and investment of the operation is lowered, construction cost can be reduced by over 30%, meanwhile, the construction period can be shortened, the construction can be carried out in safety, and the method is also an environment-friendly.