Abstract: 【Objective】The understanding of heterosis and genetic analysis of main phenotypic traits will provide a feasible guidance for tree peony breeding. 【Method】In this study, twenty phenotypic traits of F₁ progeny obtained from the cross of Paeonia ostii ‘Feng Dan’ and Paeonia suffruticosa ‘Xin Riyuejin’ were investigated in 2014 and 2015. In addition, correlation analysis and mixed genetic analysis were conducted on these phenotypic data. 【Result】 The results of heterosis analysis showed that 20 phenotypic traits were separated broadly among F₁ plants. The variation coefficient varied from 11.03% to 63.49%. Except for the traits of the flower height, petal width, petal length and pod height, the mid-parent heterotic values of the remaining 16 traits showed a significant difference at 0.01 level. Correlation analysis showed a significant positive correlation among the remaining 18 traits, except for the traits of petal length and pod height. Mixed genetic analysis revealed that the traits of plant height, crown width, shoot number, fruit stalk length, flower diameter, flowering duration, pod diameter and pod height were controlled by minor-polygene. The traits of shoot length, flower number, flower height, petal number, petal width, follicle number per pod, and per pod seed weight were dominated by two pairs of additive-dominant-epistatic major genes. For other traits, leaf length was controlled by two pairs of equally additive major genes, petal length was controlled by two pairs of equally dominant major genes, leaf width and per pod seed number were controlled by a pair of additive-dominant major genes, and per pod weight was controlled by two pairs of additive-dominant major genes. 【Conclusion】All 20 phenotypic traits showed heterosis and transgressive segregation, and some of them were controlled by major genes. These results provide a theoretical basis for further study on quantitative trait locus(QTL)analysis and molecular marker-assisted tree peony breeding.