Reproduction ability of farm animals is a quantitative trait that affects largely the husbandry productions. Progress in the study on genetic mechanism for high prolificacy in farm animals were reviewed at genome level and mRNA expression level in this paper. All these research results indicate that high prolificacy is a trait affected by a lot of genes, that is, the co-expression and interaction of these genes result in the formation of the trait. A lot of progresses have been made at all these two research levels. But differing from the genome level, the research at mRNA expression level only involves the genes expressed at special time in special tissues, and the genes directly contributed to the formation of traits. The genetic mechanism for this trait has been studying at the levels of genome and mRNA expression nowadays. With the development of sciences, new research methods for the trait will be provided, but only the combination of them with all these research levels will be the most effective.