Abstract: To provide data for further researches about the rules of poly(lactide-co-glycolide ) (PLGA) porous scaffolds degradation in vivo, the interaction between degradation of PLGA porous scaffolds and osteoblast activities of rat femur is analyzed in this study. Osteoblast of rat femur was planted in PLGA porous scaffolds. During four weeks degradation, the properties of osteoblast and PLGA had being observed and measured, including proliferation activities, alkaline phosphatase, calcium concentration, PLGAs relative molecular mass loss, mechanical tension strength and compression Young modulus. The results show that osteoblasts have high proliferation activity but low ALP activity and calcium concentration at the early stage of degradation. While during later stage of degradation, cells proliferate slowly and ALP activity and calcium concentration decrease remarkably. Relative molecular mass loss rate of scaffolds planted with cells are faster than control group. And mechanical tension strength and compression Young modulus are lower than control group. Above regularities indicate that PLGA porous scaffolds degradation has greater effect on cells during the later stage of degradation than the initial degradation, and the physiological activities of cells adhesion to scaffolds speed up the rate of degradation.