AMEC Environment & Infrastructure UK Ltd（AMEC）was commissioned by the Greater London Authority（GLA）to undertake a comparison of air quality in cities around the world. After completely considering factors of nation，geography，climate，demography and others，AMEC chooses 36 important cities to do the comparison study，named Comparison of Air Quality in London with a Number of World and European Cities. The report develops an air quality index to rank the cities basing on the justifiable and consistent urban monitored air quality data. Two cities from China listed on the report Beijing and Shanghai，they rank at the lowest level among 36 cities，and they have to action.