Abstract: In order to balance the mechanical strength and the biocompatibility, the calcium alginate hydrogel/poly L-lactic acid (CA/PLLA) composites were prepared. The macroporous PLLA scaffolds were fabricated using chemical foaming approach combined with the freeze-drying and particle-leaching method. Afterward sodium alginate, calcium carbonate and glucono-delta-lactone (GDL) were selected to produce the calcium alginate hydrogel using in-situ transformation method in the pores of the PLLA scaffolds. The surface structure, mechanical strength and the biocompatibility were explored by SEM, compressive strength test and the cell culture. The results show that the porous structure and the interconnected pore channels of PLLA are observed, showing that the diameter of the pores is below 2 mm, in which the calcium alginate hydrogel is capable of distributing evenly. The compressive strength of the composite material (2.74 MPa) is far better than that of the pure calcium alginate hydrogel(0.10 MPa). Chondrocytes are grown clustered and round in the composite scaffolds, resembling the growth state in natural cartilage lacuna. The CA/PLLA composite material, which is a combination of hard and soft materials and a hybrid of natural and synthetic polymers, with promoted mechanical strength and biocompatibility, can be researched further as a promising bone and cartilage repair material.