Abstract: Objective　To study the effect of alginate purity on implanted microcapsules and the function of human fetal parathyroid tissue in microcapsules.Methods　Microcapsules and microencapsulated human fetal parathyroid tissue produced with purified and unpurified alginate were xenografted into the peritoneal of mice which were divided into 4 groups. Transplanted empty microcapsules were established as control. Human parathyroid was measured to identify the secretory function of microcapsulated human parathyroid and the morphological changes of microcapsulated tissue were observed.Results　Two months after transplantation, there are significant differences in secreting function of microencapsulated parathyroid tissue between purified and unpurified groups(P＜0.05),(38.8±13.7) pg/ml and (1.2±0.7) pg/ml respectively. The retrieve rates of purified and unpurified alginate empty microcapsules are （72±18）% and (24±13）%，（65±21）% and 0 respectively after 1 and 2 months of transplantation.Conclusion　Microcapsules produced with purified alginate have good biocompatibility, the survival time of parathyroid tissue in the purified microcapsules was prolonged significantly.