The Guangdong-Hong Kong-Macao Greater Bay Area is an area with a high degree of internationalization, resource integration, economic value and benefits. More attention should be paid to its environmental risks and prevent threats to regional ecosystems and the health of the local people. The risk sources and receptors of emergently environmental events in human-intensive areas are extensive and complex, which makes the environmental risk assessment using traditionally statistical data and technical methods increasingly be subject to the criticism for its lack of timeliness and accuracy. Mobile phone signaling data has many advantages, including large sample volume, low collection cost, and strong following performance. Thus, this study attempts to introduce mobile phone signaling data and its simulated analysis of population data, and embed it into a grid-based environmental risk analysis method to assess the atmospheric environmental risk of Jiangmen City in the Guangdong-Hong Kong-Macao Greater Bay Area, describe the spatial distribution of regionally environmental risks features, and accurately identify the type of regionally environmental risk. The grid-based environmental risk analysis is a process of dividing the assessment area into grids, then quantifying the environmental risk field strength and environmental risk receptor vulnerability of each grid and calculating the grid environmental risk value according to the risk field theory and the environmental risk receptor vulnerability theory. Jiangmen City is located in the key node of the Guangdong-Hong Kong-Macao Greater Bay Area, which is an important gateway between the Pearl River Delta region and western Guangdong. It is also a well-known "overseas capital" in China. The research on Jiangmen City is typical for studying the regionally environmental risk management of the Guangdong-Hong Kong-Macao Greater Bay Area. The research method is based on the premise of following the "Recommended Methods for Risk Assessment of Environmental Emergencies in Administrative Regions", a comparative analysis of Jiangmen's population spatial distribution, atmospheric environmental risk vulnerability, and environmental risk values, obtained from statistical data and mobile phone signaling data, the results show that the overall trends are consistent. However, the results of environmental risk levels obtained by using mobile phone signaling data are more refined, with higher resolution, stronger timeliness, and more efficient data processing. The research has shown that the analysis based on mobile phone signaling data significantly improved the accuracy of the risk recipient population analysis of environmental risk assessment, which could provide an accurate reference for predicting and managing regional environmental risks, and realize the specific and minimization of emergency response areas for environmental emergencies, thereby reducing emergency treatment costs.