Highperformance liquid chromatography-UV-mass spectrometry (HPLC-UV-MS) was used to check the distribution and accumulation trends of catalpol in Rehmannia species cultivated in the same place. It reveals for the first time that all the 6 species of Rehmannia contain plenty of catalpol, with R.solanifolia, R. elata and R. piasezkii among the most, close to that of R.glutinosa. And, in root tubers of all the Rehmannia species, mature plants before winter bear most catalpol, compared to that of young seedlings and that of plants in blossom. On the contrary, in stems and leaves, plants in blossom contain most catalpol. Within each species, stems and leaves usually have more catalpol than that of root tubers, enlarged and low lignified root tubers accumulate more catalpol than that of thin and high lignified ones. The mechanism of distribution and accumulation trends of catalpol and expected application of the resource species have been discussed.