Background: Human neural stem cells (hNSC) transplantation has been used for the treatment of neurological injury and neurodegenerative disease and has produced some desired effects, but the beneficial effects are limited and the long-term effects remain unknown because the best time for NSC transplantation after hypoxic-ischaemia (HI) is unclear. Objectives: This study was designed to investigate the changes in NSC after cerebral HI-damage, and to provide a theoretical reference for NSC' therapeutic benefits to the HI-damaged brain. Methods: 210 seven-day-old Sprague-Dawley (SD) rats were randomly assigned into three groups: a HI group, a hypoxic group and a normal control group. They were subdivided into 7 time point groups: 3-hour, 6-hour, 1-day, 3-day, 7-day, 14-day and 21-day. Cells were stained for Nestin, a representative protein of NSC. The counts of immunoreactive cells were made under a light microscope, photographed at 400X magnification and counted in ten random different visual fields per section. Results: The results showed that: (1) In normal controls, hypoxic groups and HI groups, there was NSC organisation in SD rat brains at 3-hour, 6-hour or 1-, 3-, 7-, 14- and 21-day time points. (2) NSC were reduced at 2 weeks of life in the normal control group, and reduced to the lowest number at 3 weeks after birth, presenting a trend of NSC gradually reducing with age. (3) Hypoxia can improve NSC proliferation to some degree, but proliferation begins to decrease with development of the HI. Conclusions: The results provide reference value for selecting the best treatment time window of NSC transplantation for the treatment of neonatal hypoxic-ischaemic brain damage.