A conventional heat pump is unable to meet the heating requirement in cold regions, because its heating capacity decreases rapidly when ambient temperature is below –10oC. This paper presents a new heat pump cycle that can secure heating capacity under low ambient temperature by employing the scroll compressor with supplementary inlets. When the heat pump works in low temperature environment, the refrigerant from the condenser is injected in the compression chambers via the inlets to improve working process of the scroll compressor, so that the performance of the heat pump is increased quickly. The heat pump prototype was experimented and the measured results demonstrate that the heat pump can realize high temperature water supply and high capacity even under the low ambient temperature of -10 oC ~ -15 oC. The developed heat pump system can be used for heating in cold regions.