The scroll compression with vapor injection is applied to under-floor heating system to solve the problems of poor heating performance and instability operation under the condition of low ambient temperature in this paper. The compressor discharge temperature，heating performance

power consumption and COP（Coefficient of Performance） are researched and compared with the heating system without vapor injection. The results show that under the ambient temperatures between -20 ℃ and 7 ℃

the under-floor heating system based on vapor-injection compressor has a higher heating capacity and COP compared with the normal heating pump

and the heating capacity is increased by 26.2%

and the COP is increased by 8.7% on average

and power consumption is only increased by 16% on average; and when the ambient temperature is -20 ℃

the discharge temperature is decreased 12 ℃.The experimental results demonstrate that the under-floor heating system based on vapor-injection compressor can better satisfy the demands of low ambient temperature with low energy consumption.