Objective Calcium phosphate bioceramics has a broad appl ication prospect because of good biocompatibil ity, but porous scaffolds with complex shape can not be prepared by the traditional methods. To fabricate porous calcium phosphate ceramics by rapid prototyping and to investigate the in vitro osteogenic activities. Methods The porous calcium phosphate ceramics was fabricated by rapid prototyping. The bone marrow mesenchymal stem cells (BMSCs)were isolated from bone marrow of Beagle canine, and the 3rd passage BMSCs were seeded onto the porous ceramics. The cell/ceramics composite cultured in osteogenic medium were taken as the experimental group (group A) and the cell/ceramics composite cultured in growth medium were taken as the control group (group B). Meanwhile, the cells seeded on the culture plate were cultured in osteogenic medium or growth medium respectively as positive control (group C) or negative control (group D). After 1, 3, and 7 days of culture, the cell prol iferation and osteogenic differentiation on the porous ceramics were evaluated by DNA quantitative analysis, histochemical staining and alkal ine phosphatase (ALP) activity. After DiO fluorescent dye, the cell adhesion, growth, and prol iferation on the porous ceramics were also observed by confocal laser scanning microscope (CLSM). Results DNA quantitative analysis results showed that the number of BMSCs in all groups increased continuously with time. Plateau phase was not obvious in groups A and B, but it was clearly observed in groups C and D. The CLSM observation indicated that the activity of BMSCs was good and the cells spread extensively, showing good adhesion and prol iferation on the porous calcium phosphate ceramics prepared by rapid prototyping. ALP quantitative analysis results showed that the stain of cells on the ceramics became deeper and deeper with time in groups A and B, the staining degree in group A were ber than that in group B. There was no significant difference in the change of the ALP activity among 4 groups at the first 3 days (P gt; 0.05); the ALP activity increased obviously in 4 groups at 7 days, group A was significantly higher than other groups (P lt; 0.05) and groups C, D were significantly higher than group D (P lt; 0.05). Conclusion The porous calcium phosphate ceramics has good cytocompatibil ity and the designed pores are favorable for cell ingrowth. The porous ceramicsfabricated by rapid prototyping has prominent osteogenic differentiation activity and can be used as a choice of scaffolds for bone tissue engineering.