Drop is a frequent cause for infant head injury. To date, finite element (FE) modeling was gradually used to investigate child head dynamic response under drop impact conditions, however, two shortages still exist on this topic: (1) due to ethical reasons, none of developed 6-month-old (6MO) head FE model was found to be quantitatively validated against child cadaver tests at similar age group; (2) drop height and impact surface stiffness effects on infant head responses were not comprehensively investigated. In this study, motivated by the recently published material properties of soft tissues (skull and suture, etc.) and reported pediatric head global cadaver tests, a 6MO child head FE model was developed and simulated results compared with the child cadaver experimental data under compression and drop conditions. Comparison of results indicated that the FE model showed a fairly good biofidelic behavior in most dynamic responses. The validated FE model was further used to investigate effects of different drop heights and impact surface stiffness on the head dynamic responses. Numerical results show that the pediatric head mechanical parameters (peak acceleration, HIC, maximal vonMises stress and maximal first principal strain of skull) keep increasing with the increase in drop height, and exhibit “logarithmic function” shapes at “fast–slow” trends with increase in impact surface stiffness. Based on above analysis, the regressions were conducted to describe the relationship between drop height and impact surface stiffness and head global injury predictors (head peak acceleration, HIC, etc.). This paper provides a fundamental study of child head injury mechanism and protection under drop conditions.