Abstract: Dan 340 is a high quality serf-bred line of maize,which selected by self-axle Lu 9 as a female parent and shelled maize as a male parent.The self-bred line is a motive force to breeding and production of maize in our country.The writer not only looked up the technical literature and sorted out the data meticulously on Dan 340 and its derived line,but also analysed its heterosis utilization models.