Thai consumers prefer meat from Thai native chicken. The several studies showed that they have good meat texture led to a good taste and low cholesterol content compared with commercial broilers (Wattanachant et al., 2004; Jaturasitha et al., 2008). However, Thai native chicken have been low growth rate and low number of egg production. From this reason, animal breeders are required to improve these traits via the selection and mating plan. In theory, the number of parents in based population (G0) related with an effective population size (Ne) (Falconer and Mackay, 1996). The objective of this study was to compare genetic response of growth traits in Thai native chicken under index selection based on the difference number of sires and dams and selected to short term (5 generations) and long term (10 generations)