In order to study the mechanism of the inhibitory effect of salvia miltiorrhiza (SM) and tetramethyl pyrazine (TP) on scar fibroblast, the DNA content of fibroblast and the all distribution in cellular cycle was measured by FCM. The hypertrophic scar tissue of chest was chosen for primary culture of fibroblast. Then this cultured cell was reacted with SM and TP. FCM was used to measure the DNA index and duration of cellular cycle. The results showed that: 1. SM and TP had little effect on DNA index, but when the concentration of drugs reached the threshold, they could increase the amount of fibroblasts in C2-M stage and the duration of G2-M stage was prolonged; 2. TP could also prolong the duration of S-stage; 3. SM and TP could prolong the multiplication time of fibroblasts and this effect was correlated postively with the dosage of drug. The conclusions were that the inhibitory effect of SM was the result of inhibiting the mitosis of cells and the cellular cycle be at a standstill in G2-M stage. The inhibitory effect of TP was due to the inhibition of synthesis and duplication of DNA and cellular mitosis, and the cellular cycle was also at a standstill in G2-M stage.