I'm using TG1 one strain of E-coli but it grows in kanamycin
plates.Why?

Hello F2:

From what I can tell most of the E. coli TG1 strains do not contain the kan gene

Please refer to this E. coli strains and genotypes link.

Are you certain that your genotype does not contain kanamycin resistance? If so, then maybe you will need to adjust your drug concentrations.