Abstract: Robert Koch (1843-1910), a German doctor in the 19th century, was the founder and pioneer of world pathogenic bacteriology, as well as an expedition to infer the causes of epidemics. He innovated the technology of mycobacterium tuberculosis staining, developed solid culture medium, microphotography and bacterial microscopy, etc., which laid the foundation for researchers in microbiology; he successively found more than 100 kinds of bacteria, such as anthrax, typhoid, tuberculosis and vibrio cholerae, which opened the mysterious veil of unknown causes diseases; the single cause biological specific causation theory and Koch's law came out, which opened the "golden era" of epidemiological causal inference.