Strict carbon emission regulations are set with respect to countries’ territorial seas or exclusive economic zone shipping activities to meet their climate change commitment under the Paris Agreement. However, no shipping carbon mitigation policies are proposed for the world high sea regions, which results in carbon intensive shipping activities on high seas. In this paper, we propose a Geographic-based Emission Estimation Model (GEEM) to estimate shipping GHG emission patterns on high sea regions. The results indicate that annual shipping CO2-e emissions on high seas reach 211.60 million metric tonnes in 2019, accounting for about one-third of all shipping emissions globally and exceeding annual GHG emissions of countries such as Spain. The average emission from shipping activities on high seas is growing at approximately 7.26% per year, which far surpasses the global shipping emission growth rate of 2.23%. We propose the implementation policies on each high seas region with respect to the main emission driver of each high seas identified from our results. Our policy evaluation results show that carbon mitigation policies could reduce 25.46 and 54.36 million tonnes CO2-e in the primary intervention stage and overall intervention stage respectively, with 12.09% and 25.81% reduction rates in comparison to the 2019 annual high seas shipping GHG emission.