Abstract: Chicken embryos from stage 15 to stage 45 were studied by means of serial section and light microscopy in order to learn the relationship between the spermatogonium and the testicular development in the early chicken embryo. The results showed that: At the stage 22~28 (3.5~5^th hatching day), the glycogen in the PGCs cytoplasm reduced gradually. On the stage 29(6^th hatching day), the gonad of the embryo appeared the feature of testis, and the glycogen in the PGCs cytoplasm reduced further. On the stage 31 (7^th hatching day), the differentiation of ovary or testis was obvious and the glycogen in the PGCs cytoplasm later disappeared. On the stage 34(8^th hatching day), the testicular cord had been begin to differentiating. The every cord had been solid tube with the spermatogonium. On the stage 35~37 (9~11^th hatching day), the number of testicular cord had been increased with the ages of embryonic development. The spermatogonium were monlayer located in cord. In this stage, the fewer sustentacular cells had been differentiated, while difficult to distinguish. On the stage 38~40 (12~14^th hatching day), the seminiferous had been formed typically, the number of spermatogonium increased as well as sustentacular cells, and the interstitial cells in seminiferous distributed in groups. On the stage 40~45 (16~19^th hatching day), the testis on the right was a little bigger than that on the left, the number of spermatogonium increased obviously and showed likely clusters of grape in the middle of seminiferous.