The study aimed to explore the effect of developmental histomorphology of rat hippocampus after early stage yttrium exposure.Methods Rats were dietary exposed to yttrium nitrate under one of four doses (0,2,8,2 mg/kg BW, calculated based on Y³⁺) from GD0 to PND70, based on the developmental neurotoxicity. Six offsprings'(half male and half female)hippocampi per group were selected for histomorphology observation by the method of DAPI stain. Nerve special dyeing and HE staining was applied and subcellular structure was observed by transmission electron microscope.Results The amount of hippocampus glial cell apoptosis was significantly increased in 32 mg/kg BW group as compared with the control. No obviously visible change of nerve fiber and neuronal Nissl body in hippocampus was found. However, the impaired integrality of blood-brain barrier, swelling mitochondria and deposit sediment of dense particulate matter were found in 32 mg/kg BW group.Conclusion Rats exposed to yttrium of 32 mg/kg BW from GD0 to PND70 caused apoptosis of hippocampus glial cell, the impaired integrality of blood-brain barrier and the oxidative damage of mitochondria.