Modified polyglycolic acid (PGA) was prepared by melt blending and reactive extrusion. The effects of chain extenders, crosslinking agents and lubricants on melt fluidity, dynamic rheological properties, thermal stability, and crystallization properties of modified samples were studied. The results show that the melt strength of samples are significantly improved by using ADR chain extender and BIBP crosslinking agent simultaneously, the melt mass flow rate is decreased by 73.6% compared to pure PGA. The thermal stability of modified samples is also improved, with increasing the 5% thermal decomposition temperature by 7 ℃. With the addition of chain extender and crosslinking agent, the degree of crystallinity of PGA samples are decreased, the number of crystal nuclei are decreased, and the spherulite size are increased. The degree of cross-linking of the sapmles with adding chain extender and crosslinking agent at the same time is increased, resulting in imperfect crystallization and the formation of irregular crystals. Molecular motion are promoted by lubricants, and the crystallization temperature of PGA sample is decreased from 179.3 ℃ without addition to 173.9 ℃ after addition.