This is a longitudinal study of motor development of infants from birth to one year old.28 infants were selected as subjects from "A Cross-sectional Study of Motor Development of Infants from Birth to One Year Old. (Su, et, al, 1982)" Each subject was observed in his or her home monthly. Mean, standard deviation, linear regression, repeated measures two-factor ANOVA, simple main effects and q-test, were used in the statistics and analysis of data. Results show that age of the subjects is a very important predictor to the motor development of infants. Sex is not an important factor. It´s obvious that maturation is an important factor to determine the pattern and rate of motor development. The data of motor development in this longitudinal study are close to the data of cross-sectional study of motor development by Professor Su et al. in 1982. All of infants´ motor development is orderly, just like the development pattern of motor characteristics in Gesell´s study in 1929. In this study, we have found early stimulation has great influence on the development of infants, and good nutrition is important too.