The paper aims to explore the effects of transplanting period on the growth, development and yield of Codonopsis pilosula in the semi-arid area of the Loess Plateau, so as to provide theoretical basis for high-yield cultivation of C. pilosula. In 2020, the stages transplanting experiment of C. pilosula was carried out in Dingxi City, Gansu Province. The three transplanting periods were designed, with the traditional transplanting period as the control (CK, transplanting on April 1), and delay the traditional transplanting period by 5 days (T1, transplanting on April 6) and 10 days (T2, transplanting on April 11). The characteristics of growth and development, biomass accumulation and yield of C. pilosula at different transplanting periods were analyzed. The results showed that the difference of emergence time of branching stage in different treatments was the largest, and T2 treatment was delayed by 5 days and 2 days compared with CK and T1 respectively. The transplanting period was delayed, the growth period was shortened, and the rapid growth period of root was advanced. The initial growth potential (C0) was increased, and T2 treatment was 24.72% and 6.65% higher than CK and T1. The duration of gradual growth period was significantly shortened with the delay of transplanting period, and the duration of rapid growth period had little difference between different treatments. The average root growth rate (Va) of T1 treatment was 3.73% and 2.45% higher than CK and T2. The accumulation of dry matter and its growth rate in rapid growth period were the highest. The maximum growth rate (MGR) of aboveground biomass showed that T2> T1> CK, T2 increased by 17.29% and 10.46%, compared with CK and T1. C0 and Va were the largest, C0 in T2 treatment increased by 7.74% and 10.32% compared with CK and T1 respectively, and Va increased by 19.67% and 12.30%. The transplanting period was delayed, the growth duration of different growth period of aboveground biomass was shortened, and the dry matter accumulation amount and its accumulation rate were increased accordingly, and the yield of C. pilosula was increased, the yields of C. pilosula in CK, T1 and T2 were 257.67, 306.68 and 524.90 g/m2 respectively. The yield of T2 was 104% and 72% higher than CK and T1 respectively. The results can provide reference for high-quality cultivation of C. pilosula and improving the utilization rate of climate resources in the semi-arid area of the Loess Plateau.