Records of precipitation in Macau are collected from three local monitoring stations from 1993 to 2003. Chemical compositions of precipitation are analyzed to reveal the causes of wet deposition inMacau. The review of volume weighted annual pH values over this period shows that the entire area of Macau 2 is subjected to acidic precipitation. The concentrations of three ionic species H+, SO42- and NO3- are analyzed statistically and their distributions are found to have positive skewness and kurtosis. Lognormal cumulative distribution function fits each sample cumulative distribution function for each ionic species well implying that their temporal behaviours are governed according to the lognormal distribution. Nonetheless, the distribution of each ionic species exhibits spatial variability across the stations. Therefore, it is suspected that the sources of wet acid deposition indifferent parts of Macau are different and further correlation analysis on the values of pH, sulfate, and nitrate of the precipitation is carried out. Correlation analysis on the values of pH, sulphate and nitrate of the precipitation shows that the linear correlation between [H+] and [SO42-] is higher than the linear correlation between [H+] and [NO3-] at two of the monitoring stations. The result indicates that sulfur dioxide could be the main contributor of acid wet deposition in Macau as suggested by previous preliminary studies. In addition, the eleven-year averaged ratio of [SO42-]/[NO3-] at Ka-Ho being 5.06 reinforces this conclusion. However, differences in the linear correlation between [H+] & [SO42-] and [H+] & [NO3-] among the three monitoring stations are found. Therefore, it confirms the aforementioned suspicion, that the sources of wet acid deposition in different parts of Macau are different. The wet acid deposition in Macau is then believed to be controlled by local sources ofsulfuric acid, nitric acid and some other acids that are not accounted for in the present study. Finally, the ratios Of [SO42-] ON and [NO3-]/[NO2] are found to decrease generally with the rainfall volume at Ka-Ho and Talipa Grande. Hence, it is concluded that longer rainfall duration can help to reduce the acidity in rainwater.