Earworm is very useful animal in soil ecosystem, however it is harmful for golf courses because they introduce many cast on turfgrass that reduces turf uniformity and play quality. However, no information has found on earthworm diversity and seasonal fluctuation in different Korean golf courses. In this study, we focused to carry out earthworm species composition and seasonal population structure in turfgrass of golf courses. During spring and fall season survey with direct digging and tea saponin drenching sampling in 5 different golf courses, 6 species under 3 families of earthworms were collected. Earthworm species composition and density was different among the golf courses. Aporrectodea caliginosa in Lumbricidae was dominant species in Anseong and Dongrae Benest Golf Club; however Amynthas carnosus in Megascolecidae was dominant species in Anyang and Glenrose Golf Club. Ap. caliginosa was collected only aclitellum in July and Am. carnosus was collected aclitellum and clitellum in August in golf courses. Seasonal population of earthworm was different depending on earthworm species (Am. hupeiensis was the highest in August and Ap. caliginosa was in April) however small number of collected earthworm species were not dominant trend in golf courses.