The addition of intumescent flame retardant to PLA can greatly improve the flame retardancy of the material and inhibit the dripping, but the major drawback is the adverse impact of the mechanical properties of the material. In this study, a small amount (less than 1.5wt%) of DCP and TAIC with a specific proportion were added to form a cross-linking structure in the flame retardant PLA, so as to improve the flame retardant and mechanical properties of the material simultaneously. The increase of torque and the decrease of melt flow rate indicated that the crosslinking structure can be formed in the system by adding 0.9wt% DCP and 0.3wt% TAIC. The gel content of the material is 30.8% after the addition of DCP and TAIC. Then, the effects of the cross-linking structure on the mechanical properties, flame retardancy and thermal properties of flame retardant PLA were studied.