A new and efficient method for isolation of plant RNAs was developed by adding bentonite into extraction buffer in order to get rid of protein and restrain Rnase. The electrophoretic patterns of nucleic acids and absorbance at 230 nm, 260 nm and 280 nm in a UV-Vis spectrophotometer revealed the extraction with this method can obtain RNAs with good integrity and purity without any apparent DNA contamination from the plant materials rich in with polysaccharide and polyphenol like Jatropha curcas leaves, to which TRIZOL reagent, SDS-KAc solution and Guanidine isothiocyanate solution failed. Furthermore, the result of nuclear gene (18 S rRNA gene) amplified by RT-PCR indicated that the RNAs prepared with this method can meet the needs of most molecular biological experiments including gene cloning and expression analysis.