Objective To investigate the feasibility of extraction site preservation using injectable calcium phosphate cement (CPC) combine with poly (lactic-co-glycolic acid) (PLGA) microspheres.Methods Immediate extraction defects models were created in canine mandibles,and the defects were filled with CPC/PLGA (experimental group,E),Bio-Oss (positive control,P),non-treatment (blank control,B) respectively.Dogs were sacrificed after 4,8,12 weeks post operation.Statistical analysis were conducted using SPSS 19.Results Results of radiological observation showed that there were not significantly different between groups in 4 and 8 week(P ＞0.05).After 12 week,E(114.9 ±8.4)were not significantly different compared with P(117.4 ± 12.1) (P ＞ 0.05),both were significantly higher than B (95.0 ± 12.6)(P ＜0.05).Histology examination showed that at 4 week following surgery,the result of newly formed bone was as follow,P [(87.5 ± 1.5) ％] ＞ B [(78.7 ± 2.7) ％] ＞ E [(69.2 ± 1.8) ％] (P ＜ 0.05).At8,12 week,results of P[(94.0 ±2.3)％ and (93.5 ±1.9)％]and E[(94.7 ±1.1)％ and (96.0±0.9)％] were better than those of B[(76.8 ±3.0)％ and (87.0 ±2.4)％] (P＜0.05).Conclusions The effect of CPC/PLGA repair immediate alveolar ridge defects is the same as that of BioOss,and CPC/PLGA can be used as a material in extraction site preservation.