Abstract: The genetic basis of parental combining ability of hybridization between Alnus plants was studied to provide a theoretical basis for the selection of parents for interspecific hybridization of Alnus plants. Using two A. cremastogyne species, four A. formosana species, and three A. glutinosa species as hybrid parents, 18 hybrid combinations (3 × 6) were configured according to incomplete random mating design (NCⅡ) to calculate the genetic parameters and competitive advantages of 9 seed and fruit traits such as general combining ability (GCA), special combining ability (SCA). The results showed that there were significant genetic differences in seed and fruit traits of Alnus interspecific hybrid combination. All kinds of seed and fruit traits were mainly characterized by gene additive effect inheritance, and seed length, seed width, and 1000-grain weight were jointly controlled by gene additive effect and non-additive effect. The narrow heritability order of seed and fruit traits was FWH>FWH>FL>WTS>SL>SW>CL>SSF>SA. The GCA value between parents and SCA value between hybrid combinations were quite different, and there was no correlation between GCA and SCA. Among the tested 18 hybrid combinations, ACjt04, ACjg00, and AFhlt01, AGtc02 had higher GCA and SCA values in seed and fruit traits, and could be selected as excellent parents accessions. The competitive advantage of 9 seed and fruit traits of 18 hybrid combinations had positive correlation with GCA and SCA, and the correlation with SCA was higher than GCA. Comprehensive analysis showed that the competitive advantage of Alnus interspecific hybrids had close genetic correlation with GCA and SCA. The selection of high GCA parents and high SCA hybrid combinations was the key to the interspecific hybridization breeding of Alnus with strong dominance.