Crucian carp (Carassius auratus) is an important aquaculture species, in which diploid, triploid and tetraploid forms coexist. Diploid crucian carp reproduce sexually, while both triploid and tetraploid crucian carp reproduce via gynogenesis. Because only females passed their genome to the next generation, gynogenetic fishes are usually all female and reproduce clonally. However, there are unusual high proportion of males in natural populations of triploid crucian carp. Triploid crucian carp (Carassius auratus) reproduce thorough gynogenesis with unusual high proportion of males in its natural population. These males have normally developed testis, which can generate viable sperm. Additionally, DNA content of sperm was about half of that of somatic cell, which indicated that meiosis has occurred during spermatogenesis of triploid crucian carp. The average DNA content of a cell population can be accurately can be determined by flow cytometry, but it is difficult to detect the change of certain chromosome in the individual sperm. To answer the question whether or not the sperm of triploid crucian carp is aneuploidy, it is necessary to quantitatively analysis the genetic composition of single sperm. In this study, microsatellite markers were used to genotype a hybrid family between female common carp (Cyprinus carpio) and triploid crucian carp (Carassius auratus), the results are were as follow: the alleles of dam Cyprinus carpio showed mendelian segregation patterns in the offspring; the sire triploid Carassius auratus contained three genomes of Carassius spp. and alleles of the sire showed random segregation patterns. These results suggested that: triploid crucian carp originated from diploid crucian carp by autoduplication, rather than the hybridization between diploid Cyprinus carpio and Carassius auratus. Our results also indicated that; triploid crucian carp generated aneuploid sperm by random segregation of chromosomes which is similar to other triploid fishes, rather than generated reduced sperm through equal meiosis. In a wordsummary, triploid Carassius auratuscrucain carp is a unique bi-sexual fish that reproduce by gynogenensis but did not originate from interspecific hybridization.