Refrigerant migration and redistribution will occur during the on-off processes of a refrigerating system. Based on a horizontal freezer BC/BD-379HBN，dynamic characteristics of the refrigerant migration and its effects on the freezer performance were studied experimentally. Results show that the process of the start-up can be divided into three stages，i.e.，refrigerant emigrating from evaporator，evaporator two-phase section increasing stage，and evaporator two-phase section stabilized stage. In the first stage，the refrigerant flowrate through the compressor was larger than that through the capillary tube，resulting in an increase in the condensing pressure. In the second stage， condenser outlet temperature stabilized gradually with the increase in the refrigerant flowrate through the capillary tube，indicating the end of the pressure-difference rebuilt process. In the third stage，a maximum cooling capacity was obtained due to the fact that the two-phase section covered the whole evaporator tube pass. The refrigerant redistribution process occupied 3.50 minutes which was about 32% of a single compressor-on period. However，the cooling capacity during this process was small. In conclusion，a large migrating loss was introduced by the start-up refrigerant migration process of the freezer.