Based on large number of research papers, this roundup was described from three aspects: (1) The general situation of studies on close hybridization of fish in China, emphatically introduced 15 kinds of hybrids, varieties and strains obtained by close hybridization, including Feng carp, He-yuan carp, Yue carp, Tri-crossed carp, Furong carp, Jian carp, Cold-resistant strain in purse red carp, Songpu carp, Xing-de carp, Red mirror carp, Blue scale carp and New GIFT tilapia, etc;(2) The application of fish close hybridization in aquaculture, for example the utilization of heterosis, induction of triploid, resistance breeding (cold-resistant, disease-resistant), breeding of new varieties, variety rejuvenation, rescue of rare varieties, and improvement of fish meat materials etc; (3) Some problems on close hybridization of fish, that is correct idea on hybridization, selection and pairs of parent, parental purity and heterosis, application of back cross and multiple cross, it is strictly prohibited for the hybrid to propagate offspring. Key words: China; fish; close hybridization; aquaculture