Due to the great genetic difference between local early maturing sorghum and exotie materiac, it is very difficult to obtain a satisfactory breeding parent from a single cross between above two kinds of genetic rosouces in the early maturing sorghum production area of north china. The problem can be solved by using the successive crossing method. In this way, it is possible to select parents material with satisfactory agronomic characters for planting in the northern part of china. In improving tropical genetic resources and making hybridic crosses, seed presenility is one of the problems often encountered. In general, the problems is related to the relationship between the parents used. The hybrids are normal if the relationships are close or the parents of a given cross are not presenile. The hybrids may be seriesly presenile if one of the parents is presenile. The maturing dates of those hybrids with some exotic pedigree are usualy significantly celayed when they are planted in cold arer, it is definntly recessary to develop varieties or hybrids which is insensitive to temperature in the northern early maturing sorghum production area of china.