The platelike bainitic ferrite growth rates were calculated by two modified diffusional models. Good agreements between experimental and theoretical results are found in Fe-0.59C wt.%, Fe-0.81C wt.% and Fe-0.478C-4.87Ni wt.% alloys. A slowing down effect due to the alloying element Mo is emphasized in Fe-0.69C-1.8Ni-0.8Mo wt.% alloy. However, the experimental data are lower than theoretical ones about two orders in Fe-C-8.7Ni wt.% alloys. According to the discussion of the results, it is suggested that the bainite transformation mechanism may relates to steel composition and transformation temperature.