To establish evaluation mechanism for structural design of asphalt foaming chamber, comparative evaluation method for analysis and experiment of multiphase flow field in asphalt foaming chamber was proposed. Modeling the asphalt foaming process, analyzing multiphase flow field distribution in different foaming chambers, comparing analytical results with experimental data, validity of the model was verified. Evaluation index of foaming chamber was built and compared with the experimental data. Evaluation mechanism for structural design of asphalt foaming chamber was obtained and to a certain extent mechanism of asphalt foaming was revealed. It is concluded that uniformity between asphalt and water is smaller and temperature fluctuation is bigger and water vapor is less, structural design of asphalt foaming chamber and foaming result is better. The method is valuable for structural design of foaming chamber and engineering applications of foamed asphalt.