Climate mitigation has become a global issue and most countries have promised their greenhouse gas reduction target. However, after Trump took office as president of the United States (US), the US withdrew from the Paris Agreement. As the biggest economy, this would have impacts on the emission space of other countries. This paper, by using the integrated model of energy, environment and economy/computable general equilibrium (IMED/CGE) model, assesses the impacts of the US withdrawal from Paris Agreement on China, India in terms of carbon emission space and mitigation cost under Nationally Determined Contributions (NDCs) and 2°C scenarios due to changed emission pathway of the US. The results show that, under the condition of constant global cumulative carbon emissions and fixed burden sharing scheme among the countries, the failure of the US to honor its NDC commitment will increase its carbon emission space and decrease its mitigation cost. However, the carbon emission space of other regions, including China and India, will be reduced and their mitigation costs will be raised. In 2030, under the 2°C target, the carbon price will increase by US$14.3 to US$45.3/t in China and by US$10.7 to US$33.9/t in India. In addition, China and India will incur additional GDP loss. Under the 2°C target, the GDP loss of China would increase by US$23.3 to US$72.6 billion (equivalent to US$17.4 to US$54.2/capita), and that of India would rise by US$14.2 to US$43.1 billion (equivalent to US$9.3 to US$28.2/capita).