Abstract: The DH population of 2 combinations had been constructed in cold rice region by the technology of anther culture in hybridization combination F1 which from 3 parents of different grain width and analyzed the hereditary variation distribution of grain width in DH population, estimated hereditary capacity and rate over parent in DH population by the model and formula which were presented by Choo and Reibergs, and examined the number of gene pairs and the pattern of gene interaction which controlled these characters. The result showed that the hereditary variation of grain width was divided into two models: Model I was mixed quantitative heredity which was controlled by major gene and many minor genes, there was no interaction of major genes. Model II was mixed quantitative heredity controlled by many major genes and many minor genes, there was effect among major genes, which was complement each other. The hereditary capacity of grain length was 0.61, and the number of gene pairs was 7.8-12.3 pairs controlled by grain length, 9.9 on average. As a result, strictly choose grain width individual of low generation was very effective for germplasm innovation, such as improving grain weight and breeding suitable grain types in quality breeding of anther culture in cold rice region. Key words: Cold region; Japonica rice; Grain Width; DH population; Genetic variation