Abstract: The aims are to clarify the genetic characteristics of cotton boll weight, and illustrate the contribution mechanism of boll weight to yield formation. RIL populations are constructed based on the national approval elite cultivar‘CCRI70’. The phenotypes of the RIL populations and their parents ’901-001’and‘sGK156’ are evaluated under 9 various environments (15AY, 15LQ, 15ALE, 16AY, 16LQ, 16ALE, 16KRL, 16SHZ and 16CD). The inheritance characteristics of boll weight are analyzed with the major gene+polygene genetic model. The results showed that the effects of different environments on boll weight had the following tendency: the Northwest Early-maturity Region > the Northwest Middle Early-maturity Region ≥ the Yellow River Basin > the Yangtze River Basin. The effects of parents on boll weight under the 9 environments showed that‘901-001’ was greater than‘SGK156’. The boll weight of RILs ranged from 3.29 g to 7.82 g, the absolute values of skewness and kurtosis were all less than 1.0, which showed a normal distribution, the coefficients of variation ranged from 5.78 % to 8.72%. The genetic model was controlled by 2-4 major genes or 2 major genes + polygenes. The maximum number of major genes was four under 15AY and 16CD environments. Generally, the inheritance of boll weight is mainly controlled by polygene model. The heritability of major genes ranges from 6.96% to 45.69% and that of polygene ranges from 51.06% to 88.99%, indicating that the boll weight are greatly influenced by the interactions of environments and genotypes.