Trichogramma dendrolimi is an important egg parasitoid widely used in biological pest control against various Lepidopteran pests. To clarify the chromosomal characteristics and the mitotic process of T. dendrolimi, the study investigated the autosomal karyotype of T. dendrolimi at prepupal stage. The karyotyptic analysis was conducted by comparing the karyotype of T. dendrolimi with other two Trichogramma species. The mitotic process of somatic cells of T. dendrolimi was observed. The results showed that the number of autosomes in T. dendrolimi was n=5, and the karyotype formula was n=4 m+t, which clarified the typical characteristics of T. dendrolimi karyotype. The mitotic characteristics and abnormalities in the mitotic process of prepupae of Trichogramma dendrolimi could be observed. The results would provide a reference for investigating the cytological mechanisms and chromosomal behaviors during the sex determination and development of Trichogramma wasps.