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In order to investigate the characteristics of temperature decreasing of mashed potatoes without packages during freezing in an air blast freezer,，a three-dimensional unsteady numerical model was established to simulate the freezing process of mashed potatoes. According to the thermo-physical properties of mashed potato, the process of the temperature decreasing during freezing was simulated by Fluent，after which the airflow information in the container was obtained．A test was done to verify the accuracy of the model,，and it was found that the simulation values and test values were in good agreement,，the maximum temperature difference between the test data and simulation result was 7.1K and the relative error of freezing time was 3.9%. After that，two design parameters (air velocity and air temperature) which would affect the freezing process were analyzed．Improving the air velocity can shorten the time of freezing but would improve the maximum temperature difference between the mashed potato’s core and edge. The variation coefficient of temperature among mashed potatoes was firstly increased and then decreased with the increase of air velocity, and it was minimum when the air velocity was 6m/s. When the air velocity was bigger than 6m/s,，the freezing rate trended to be steady along with the growing of air velocity. Reducing the air temperature can effectively improve the temperature decreasing of mashed potatoes during freezing but also would improve the variation coefficient of temperature among mashed potatoes. The results reviewed some characteristics of the freezing of mashed potatoes without packages in an air blast freezer, which can provide a reference value for the optimization of the equipments and technologies for the freezing of foodstuffs．