Epigenetic change is dynamic during germ cell development. DNA methylation and histone modification are the most important epigenetic process to regulate the gene expressions. They are very close reciprocal relationship on the specific genomic regions called CpG islands (CGI). The CGIs are located on the promoter regions and recruit various epigenetic regulators including, CFP1, KDM2A, KDM2B, TET1 and MLL. They contain a common domain which is the zinc finger CxxC domain. The CxxC domain reads non-methylated CpG and recruits other regulatory elements such as SET1, PRC, COMPASS and SIN3A to modify Histone proteins. CFP1 contains a CxxC domain. CFP1 protein therefore imposes an ability to distinguish its important regulatory element, “non-methylated CpG” from the genome. After binding the CpG, CFP1 recruits SET1 complex, which is involved in the histone H3 lysin 4 (H3K4) methylation. However, the functional consequence of CFP1 in the germ cell development remains unknown. In this study, we demonstrated that CFP1 is critical for the both spermatogenesis and oogenesis using conditional knockout system.