Abstract: Transgenic tomato plants with tobacco osmotin gene AP24 and bean basic chitinase gene Chi together with the NPTⅡ marker gene were screened by kanamycin spraying test for several generations.The transgenic offspring of single copy lines showed the expected 3 :1 segregation ratio,and absence segregation patterns for some lines were detected in T₂ seedlings,which indicated they were homozygous lines.Some of the homozygous lines were further checked on the T₃ generation.More than 8 different homozygous transgenic lines were obtained in this experiment.However,as to double copy transgenic lines,the inheritance of trangenes are complex.Multiplex-PCR analysis was introduced into investigation of abnormal transgene segregation.The accuracy of this method was confirmed by PCR analysis,it is an optimal method in rapid and large-scale screening of transgenic tomato plants with NPTⅡ marker in open field,and this method may be extend to other crops easily.