Cotton plant architecture is closely related to cultivation mode,mechanical collection efficiency and yield. Fruit branch angle(FBA)is one of the key factors that determine cotton plant architecture. Exploring the genetic characteristics on FBA of upland cotton(Gossyp-ium hirsutum)will provide important guidance for genetic breeding of cotton plant architecture. In this study,a natural population composed of 418 accessions of upland cotton from different regions,were used as the research object. Then,measuring the FBA with digital display protractor,we performed the variability and correlation analysis of FBA in different positions of cotton main stem,as well as the phenotypic description and statistical analysis of FBA of natural populations in different ecological environments. Simultaneously,the combined populations four generations(P1,P2,F1 and F2)constructed by parents with extremely different fruit branch angles were selected as the research objects,the multi-generation joint genetic analysis of FBA phenotypic traits of the four generations was carried out,and the genetic effect and heritability of major genes were estimated using the mixed genetic model of major gene plus polygenes of plant quantitative traits. Phenotypic identification analysis showed that the coefficient of variation for FBA in the natural population of upland cotton was relatively small,and the average coefficient of variation under the four environments was 5.63%. Furthermore,the middle fruit branch(the 4th-6th position from the base)angles best represented the level of FBA of the whole cotton plant. Additionally,mixed genetic model for major gene plus polygene demonstrated that the optimal model for controlling FBA was two major genes with equal additive effect,the additive effect value of major gene was 3.65,and the heritability was 90.22%. These results revealed that the FBA of upland cotton was mainly controlled by the main gene,and the heritability of the main gene was high. The above results are conducive to clarifying the genetic law of FBA of upland cotton,which is of important practical significance for molecular genetic analysis of FBA and plant architecture genetic breeding of upland cotton.