The invention provides a locked nucleotide sensitized real-time fluorescent quantitative PCR (polymerase chain reaction) detection method for detecting the colonization quantity of phytophthora parasitica in tobacco planting soil. The method is characterized in that 5.8S ribosomal RNA (ribonucleic acid) in phytophthora parasitica and an ITS (internal transcribed spacer) region fragment adjacent to 5.8S ribosomal RNA are used for designing primers; a forward primer is 5'-TGAACGCATATTGCACTTCC-3'; a reverse primer is 5'-GACAAACCAGTCGCCAATTT-3'; LNA (locked nucleic acid) modification sites are underlined. The method is characterized by obtaining a positive recombinant plasmid through common primer PCR amplification and cloning, then using a known concentration of plasmid containing a target gene as a template and also carrying out fluorescent quantitative PCR reaction on the LNA modified primers, making a standard curve graph and standard curves and determining the quantity of phytophthora parasitica in a sample to be detected by comparing the sample detection results with the standard curves. The detection method is suitable for detection of the colonization quantity of phytophthora parasitica in the tobacco planting soil, is efficient, simple and practicable, is low in price, can complete detection within 4-5 hours, has higher detection sensitivity and can play a certain role in prevention and control of black shank in China.