Provided is a method for culturing immature oocytes. The method can promote in vitro maturation of the immature oocytes, and specifically comprises using follicular cells and a culture medium for culturing same. The culture medium for culturing the follicular cells contains CNP or variants thereof or analogues thereof and an HDAC (histone deacetylase) inhibitor. Also provided are the in vitro maturation culture medium containing CNP or variants thereof or analogues thereof and the HDAC inhibitor, and related compositions thereof, and the use of the above medium, culture medium and compositions in the promotion of in vitro maturation of the immature oocytes.