Abstract: Take 4 different kinds of potted trees including Sabina chinensis, Pinus bungeana, Sophora japonica and Fraxinus chinensis as the research objects. We have processed the sample by apparatus of microwave and have measured the content of heavy metal by inductively coupled plasma mass spectrometry (ICP-MS). Then we calculated the ecological conversion rate of Cr and Pb of leaves of 4 kinds potted trees in different site. The results showed that there were significant differences among the ecological conversion rate of Cr and Pb of different tree species. Among them, the highest ecological conversion rate of Cr and Pb were respectively F.chinensis (99.4%) and P.bungeana (98.3%) in Beijing botanical garden. The highest ecological conversion rate of Cr and Pb were respectively S.chinensis and P.bungeana in Xishan National Forest Park, ecological conversion rate were 96.4% and 94.9% respectively. In Songshan National Nature Reserve, the highest ecological conversion rate of Cr was S.chinensis (89.0%), while the highest ecological conversion rate of Pb were 2 kinds of hardwood including S.japonica and F.chinensis, both of which were 79.1%. The basic regularity of tree species′ ecological conversion was high pollutants area > low pollution area in different locations. Adsorption and purification quantity of tree species to some element is strong, of which ecological conversion rates may be weak.