Abstract: An experiment was conducted on the allelopathic effects of rhizospheric soil extracts (by water and polarity solvents) from newly planted and ratoon sugarcane (“FN28”, “GZ18”) and non-sugarcane (CK) soils. Putative allelochemicals of the rhizospheric soil extracts were then identified via GC-MS. In comparison with CK, high concentration water extracts inhibit lettuce growth whereas low concentration extracts promote growth. Inhibitory effects of rhizospheric soil water extracts of ratoon sugarcane are higher than that of newly planted sugarcane. Rhizospheric soil extracts from newly planted and ratoon sugarcanes by weak polarity petroleum ether and ether solvents promote lettuce growth. The reverse is true for extracts by medium polarity chloroform and strong polarity methanol. Further allelochemical analysis suggests that inhibitory effect of methanol extract is the strongest. Allelopathic effect of rhizospheric soil of “GZ18” is higher than that of “FN28” both by water extracting and polarity solvent extracting. GC-MS analysis of methanol extract substances from “GZ18” rhizospheric soils shows 54 compounds related with allelopathy, including acids, terpenoids, phenols, steroids and esters.