Abstract: Single factor randomized block design is used to study the effects of different planting densities on yield, output value, and yield component factors, thus to obtain the most optimum one under seedling transplanting condition. The results showed that the effects of planting densities on dried flower yield, unit output value, pyrethrin production reached extremely significant level in parabolic curve relationship. And the effective pedicel number was the most important factor affecting both dry flower and pyrethroid yield. The results also showed that the plant density was negatively correlated with the effective pedicel number, the flower number and the percentage of useless pedicel and bud per plant. However, there was a Logistic function relation between the planting density and the number of effective pedicels and flowers per unit area. In addition, the growth period of Pyrethrum cinerariifolium was shortened with the increase of planting density, while the morbidity of root rot was positively correlated with the increase of planting density. In considering the yield, output value, period of growth, morbidity and plant height, the best planting density is 60000-90000 plants/hm2 under floating-seedling transplanting condition in P. cinerariifolium planting area of Yunnan.