In this study， interspecific hybridization between Brassica napus L.（ 2n=38， AACC） and Brassica rapa L.（ 2n=20， AA） was performed， followed by cytological and molecular analyses of the progenies at the early generations in order to achieve rapidly acquisition of novel B. napus L.. The results showed that the F1 plants obtained from the crosses between B. napus L. and B. rapa L. represented 29 chromosomes and low pollen fertility， with the phenotypic variation largely derived from the female parent B. napus L.. In F2 plants， the morphological and cytological analyses revealed a proportion of plants with the B. rapa-like phenotype carrying 20 chromosomes（ 2n=20， 1.64Ⅰ +9.11Ⅱ +0.04Ⅲ in pollen mother cells（ PMCs） at diakinesis）， as was that of the parental line B. rapa L.. F2 plants carrying 24-28 chromosomes was intermediate for phenotype， while the remaining plants with 29-38 chromosomes showed the phenotype similar to B. napus L.. A few plants containing 38 chromosomes presented low seed-set after self-pollination， and the chromosomes pairing configuration was 0.68Ⅰ +18.23Ⅱ +0.30Ⅲ . The B. napus-like F3 plants were all derived from such F2 plants， and the F2 plants with 2n=35-36 gave ~40% F3 progenies with 2n=38. It could be concluded that the production of the B. napuslike progeny was rational via the directional selection of the F2 plants with such phenotype（ B. napus-like） and cytology（ 2n ≥ 35） . During the PMCs meiosis of F3 plants with 38 chromosomes， the pairing configuration was 0.59Ⅰ +18.30Ⅱ +0.26Ⅲ， and the number of bivalents ranged from 16-19， with mainly 19 Ⅱ accounting for 58.62%， while the number of univalents was from 0 to 3. Compared with F2 plants with 38 chromosomes， the number of univalents and trivalents decreased. In order to study the introgression of parental genetic material in the progenies， AFLP and SSR molecular markers were used for the F2 and F3 generations. The results showed that the A-genome of early maturing B. rapa L. was introgressed in the hybrid progenies of F2 and F3， accompanied by the double variation of A-genome and C-genome of hybrid progenies.