Polylactic acid (PLA) is currently the largest application of synthetic biodegradable polymer materials, so it is expected to gradually partially replace petroleum-based polyolefins and more widely used in various fields. However, the relaxation characteristics and very low crystallization rate determined by the hand-structure of PLA chain result in low melt strength and unstable molding process characteristics; Meanwhile, under rapid molding conditions such as extrusion and injection molding result in poor heat resistance, tensile strength and modulus of the specimen. These problems have become the bottleneck of PLA for its larger commercialization and high-performance application. Based on the regulation of isothermal crystallization behavior of PLA and its blends, especially the rate of isothermal crystallization and crystal morphology, the paper summarizes the progress in recent years in the regulation and its application of isothermal crystallization behavior for PLA using various modifiers, chain-construct, processing flow fields and post-treatment.