Abstract  [Objectives]  To investigate how mature Carposina coreana larvae enter the soil and construct cocoons, and the effects of soil humidity and temperature on cocoon formation, in order to better understand the overwintering habits of this pest and predict its future population size. [Methods]  Mature C. coreana larvae were observed burrowing into soil and forming cocoons under laboratory conditions. Soil humidity and temperature were set at 0%, 5%, 10%, 15%, 20%, 25%, 30% and 5, 10, 15, 20, 25, 30, 35, 40 ℃, respectively, and the soil penetration and cocooning rates of the mature larvae were recorded and compared. [Results]  Mature C. coreana larvae overwinter in cocoons in soil. Entry tunnels differed in shape and could be categorized as either flat U-type, V-type, Y-type, inverted Y-type or vertical type. Temperature and soil humidity significantly affected the time required by larvae to burrow into soil, the penetration rate, the cocooning rate and cocoon depth. Larvae could not enter the soil at soil moisture levels of 0% or 30% and the penetration rate of larvae was lowest at 10% soil moisture. The highest penetration and cocooning rates (100%) were recorded at soil moistures of 10% and 15%. The fastest penetration, and the highest penetration and cocooning rates, were observed at temperatures in the range of 10-25 ℃. At temperatures > 30 ℃, larvae entered the soil relatively quickly, but the penetration rate and cocooning rate gradually decreased if the temperature continued to increase. The cocoon depth gradually decreased with increasing soil moisture and temperature, but cocoons were never less than 10 cm below the soil surface. [Conclusion]  Soil moisture in the range of 10%-20% and temperature in the range of 10-25 ℃ are suitable for burrowing and cocoon formation of C. coreana larvae. Too high, or too low, soil moisture and temperature reduced the soil penetration and cocooning rate larvae and could even cause death.