Abstract: The colony development and resistant level of metalaxyl resistant (Mt^r) isolates, mechanism of resistance to xenobiotics, biological characteristic heredity and variation of Mt^r isolates, the virulence acting way, genetics stability of Mt^r isolates, control tactics to metalaxyl resistance were introduced in detail.The application of molecular bio-technique, such as nuclear acid molecular hybrid, polymerase chain reaction (PCR), random amplified polymorphic DNA (RAPD), restriction fragment length polymorphism (RFLP) and enzyme linked immuno-sorbent assay (ELISA), in the studies on pathogen of tobacco black shank and advances in the virulence heredity of Phytophthora parasitica var. nicotianae were also reviewd.