A strategy to improve aquaculture mollusks in genetics, which involve the theory, method, material and application system, is very important for the sustainable development of the marine molluscan breeding and industry. Selection and hybridization as the traditional way have proved effective in the genetic improvement of mariculture mollusks. The growth had increased significantly by selective breeding in oysters as well as the resisitance to MSX and QX disease. A frame chart of genetic improvement of mollusks had been derived from the breeding application of abalone and scallop. The systematic breeding with selection and hybridization has a substantial progress based on the family establishment in Haliotis discus hannai, H. diversicolor, Argopecten irradians, Chlamysfarreri and Pinctada martensii. The first self-fertilized family of bay scallop had been established in the 1999 and then a series of family lines with different traits have been succeed and formed the basic element of genetic breeding. The hybridization of Pacific abalone between diffeent populations with a large genetic distance has showed a remarkable traits. The hybrid of Pacific abalone has applied to improve the traits of growth and resistance in the aquaculture and 98 % seed used in the farming is hybrid. The hybridization among populations has used in other mariculture mollusks such as zhikong scallop, bay scallop, pearl oyster and small abalone. Hybridization among different populations and systematic and massive selection are the dominant approaches in the genetic improvement of mollusks. So far in China the material system for molluscan genetics and breeding is more considerable as well as the basic theory of beritabilily, hetemsis, inbreeding depression, genetic-environment interaction for the genetic improvement. The different lines have been produced by self-fertifization, inbreeding and crossing and some serf-fertilized lines of bay scallop have been bred to F4 successively. The color traits heritable are useful as the marker of selective breeding. It is necessary to deal with the molecular marker-assisted selection and design breeding. The molluscan mortality happened in aquaculture was mainly resulted from the physiological depression under the interaction of genetics and environment. So the phenomena of minimization and abnormal mortality in the mariculture mollusks should be described as ＂trait depression＂.