In this situation, because the electrical energy must be spent for heating, electric vehicles reduced driving range per one charge. Heating performance is studied for air-sourced heat pump system. In this study, experiment to analyze heating performance characteristics with air heat source has been done with various operating conditions, which are likely to match the air-sourced heat pump system test conditions under cold ambient conditions, such as variation of compressor rotational speed. When ambient temperature downed from 5°C to -10°C , heat capacity decreased by 54% due to reduction of refrigerant flow rate in accordance with decrease of 45% density of refrigerant. When the compressor speed increased from 2,000 RPM to 3,500 RPM, heating capacity increased by 40% due to higher refrigerant mass flow rate. However, COP of heat pump system is reduced by 26% due to additional compressor power. To improve air-sourced heat pump system's heat capacity, after simulations with the variation of operating conditions were performed, it seemed a good way to increase the compressor rotational speed to cope with comfort level in the cabin even though heating system had a little loss with respect to COP. To improve heating performance, exergy analysis was calculated so that inner condenser design needed to be revised and operating condition needed to be changed, such as air flow rate for inner condenser.