ObjectiveThis study was to investigate the dynamic of root dry weight of Salvia miltiorrhiza to provide a basis for optimal management in field cultivation. MethodThe Salvia miltiorrhiza Bunge seedlings were transplanted at three different dates November 26, 2009 （T 1 ）, March 9, 2010（T 2 ） and March 27, 2010（T 3 ）, and at three different densities 20 cm × 25 cm （D 1 ）, 25 cm × 25 cm （D 2 ）, 25 cm × 30 cm （D 3 ）. So a total of nine treatments were finally set. The samples were collected regularly for measuring the root dry weight and plotting the dynamic curves. Normalized root weight was fitted with CURVE EXPERT 1.3. ResultLogistic equation was the most superior equation, and estimated respectively two inflection points and length of fast growing time of S. miltiorrhiza. ConclusionThe fast-growing time of S. miltiorrhiza root was in 1 900 ℃·d to 2 200 ℃·d GDD.
