Abstract：In order to provide the theoretical foundation of street tree leaf-litter’s usage in the production of vegetables，the allelopathy of leaf-litter on cucumber（Cucumis sativus L.）of 6 kinds of street tree（ginkgo biloba，populous tomentosa，pinus tabulaeformis，poplar，platanus orientalis and paulownia）was investigated by means of bioassay in laboratory．The results showed that the leaf-litter of 6 street trees all have allelopathy on cucumber，but their allelopathic mechanisms and intensities were different．The 6 street trees’ leaf-litter could increase cucumber seedlings’ height，but had no effect on their germination rate and dry weight．As for the root length，leaf-litters of ginkgo biloba，populus tomentosa and pinus tabulaeformis had promotion effect，that of poplar had inhibit effect，platanus orientalis had no effect，and paulownia had promotion/inhibit double effects．The leaf-litters of ginkgo biloba and populus tomentosa could increase the fresh weight of cucumber seedlings，but that of the other 4 had no effect．The comprehensive sensitive index reflects that the allelopahy of ginkgo biloba＞populus tomentosa＞platanus orientalis＞pinus tabulaeformis＞paulownia＞poplar，the sensitivity of seedling height＞fresh weight＞root length＞dry weight＞germination rate．
