This study was conducted to determine the composition of volatile matter from leaves of Plectranthus tomentosa and the relative contribution to its aromatherapy. The dynamic headspace collection method for total dissolved solids(TDS),was used to extract volatile matter of adult P. tomentosa in good condition,and a gas chromatograph-mass spectrometer(GC-MS)was utilized to detect the composition of the extract. Results showed 44 kinds of volatile matter including eight types of compounds,such as alkanes and olefins. Also,22 types of terpenoids(relative content of 83.32%)were found with Limonene having the highest level of simple carbohydrates(relative content of 47.61%). Thus,this work demonstrated that a retention index of P. tomentosa volatile matter from leaves could provide a complementary and convenient method for accurate analysis,which may be helpful for the further exploitation. [Ch,2 fig. 1 tab. 10 ref.]