As rapid development of Macao’s economy in recent years, demand on energy dramatically increases. Both waste gas which is discharged in fossil fuel burning in the process of power generation and off-gases which is exhausted by vehicles make more and more sulfur oxides and nitrogen oxides in air; additionally, Macao is influenced by industrial waste gas from Perl River Delta region, it is not difficult to find that air quality in Macao in recent years is not good.    These gaseous compounds will acidify atmospheric moisture, and then it will become acid rain. Acid rain refer to rainfall with pH value less than 5.6, it shows the atmosphere is polluted. Now this rainfall seriously affects the environment which we need and human being, it is one of the environmental problems which are widely concerned in the world at present. Investigation and experiment show that acid rainfall with pH value less than 4.5 not only damages woods, but also greatly accelerates the corrosion rate of metal material; when pH value of rainfall is less than 4.0, damage is more serious.