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The heat transfer deterioration caused by frosting is the critical factor affecting the liquefied natural gas (LNG) vaporization efficiency of the ambient air vaporizer (AAV). In this paper, an LNG vaporization system using a solar-assisted heat pump (DX-SAHPNV) was proposed for AAV defrosting and LNG auxiliary heating, and a low-temperature LNG bypass flowing through the collector/evaporator was adopted for heat pump performance improvement and LNG preheating. Moreover, a dynamic model of the DX-SAHPNV system was established. Based on the meteorological data in Beijing, the system performance throughout the year and on typical days was analyzed, as well as the main meteorological factors effecting the system performance. Results showed the annual COP and the heat collection efficiency of collector/evporator with LNG bypass were 10.77% and 12.84% higher than that without LNG bypass, respectively. Comparing with the conventional AAV, the two-phase length of AAV in the DX-SAHPNV system was reduced by 12.7% and 20.2% on the typical winter and summer day, while the outlet LNG temperature was improved by 5.33 K and 11.56 K. The proposed system may provide a new perspective for the AAV defrosting and LNG vaporization optimization. [ABSTRACT FROM AUTHOR]