The present study aims to investigate the Modeling dynamic factors affecting fine motor development milestone of 9- 12 month old infants. The study was a descriptive- survey, that considering the type and aims of the research was considered as an applied research. To this end 283 infants were screened in regard with age and stage questionnaire. The applied measures were preparation of the home environment for the infant motor development, the parental postpartum attachment scale, Beak habitual physical activity questionnaire and General health questionnaire. Factors affecting motor activities were grouped into three sections including Individual, Environmental and Mother Factors. The related data were analyzed by independent T, MANOA, step by step regression and structural equation. The results of structural equation indicated that individual factors (0.99) has the most important effect on anticipation fine motor development (sleep position and season of birth were associated with fine motor development), after that environmental factor (-0.28) and finally mother factor (-0.09) has effects on anticipation fine milestone in 9-12 month old infants, Results of the regression showed that considering individual factors, motivation is significant and in regard with environmental factors, affordance is significant in anticipation of fine motor development milestone in 9-12 month old infants. Results of the present study were concentrated on Branfen bernner model.