The invention belongs to the plant diseases molecular detection field and relates to the early rapid molecular detection method of sclerotinia rot of colza. The invention is characterized by comprising the collection of weazen rapeseed petals, extraction of total DNA of rapeseed petals, nest-PCR, PCR amplification product analysis, agarose gel electrophoresis and result judgement. If sclerotinia sclerotiorum exists in a sample, a 292bp purpose bank may appear in the agarose gel under ultraviolet light, or else, the sclerotinia sclerotiorum does not exist. The primers of the invention can not only distinguish common plant leaf pathogenic fungi of distance relationship and different categories, such as alternaria genus alternaria sp, fusarium genus fusarium graminearum and coniothyrium genus sclerotinia sclerotiorum sclerotia coniothyrium parasitic fungi, but also can distinguish various fungi of common plant leaf fungal pathogen botrytis also belonging to ascomycotina, discomycete and helotiales with the sclerotinia species; the invention has high sensitivity, can detect the sclerotinia sclerotiorum DNA with the limit of 1fg/Mul, is rapid, and can obtain accurate detection result within 7 hours, however, at least two days or more than 1 week is needed for obtaining the detection result by using the traditional microbiology method.