Abstract: A complete diallel cross, including selfs and reciprocals, of ten parents from Liriodendron chinense, L. tulipifera and their interhybrids were conducted. The crossability and heterosis for seedtraits were studied. Analysis of variance for 1 000 samaras weight and full seeds rate revealed that the two traits are all different significantly among male parents and female parents. The correlation coefficient (r) of the two traits are 0. 0071 for female parents and 0. 664 7 for male parents. So, the trait of 1 000 samaras weight is useless in comparing the seed quality of different female parents. The crossability is different obviously among species, individuals in species, mating systems and cross in mating systems. Therefor, the crossability should be considered in parent selection of cross breeding. Three mating systems, C×Ｈ, H× C and C×Ｔ, have higher crossability. It can be used in hybrid production. Compared with the mating system of C×Ｃ, the mating system of C × T can produce the seeds with 70. 78% more higher germination efficiency, one day lesser time of average germination period and three days earlier of germination fastigium. These can be considered as heterosis in seed traits. The mating system of H× H has lowest germination efficiency, longest average germination period and latest germination fastigium. These phenomena are probably caused by selfing depressing