Macao's source water mainly comes from the West branch of Pearl River of China. Based on the monitored water quality data of raw water in Macao, this study adopted the National Sanitation Foundation Water Quality Index (NSFWQI) model to calculate the water quality index (WQI) from 2002 to 2019. The Principle Component Analysis (PCA) method was employed to select water quality parameters. The results show that the quality of raw water in Macao has been relatively stable in the period of interest and appeared an upward trend overall. The impact of influencing factors, including natural factors and human activities, on Macao source water has been discussed based on the acquired statistical results. This study can provide key intellectual and technical support for understanding Macao water quality data and their impacting factors. The potential benefits include early prediction of water quality issues and enhanced operational management in drinking water treatment plant.