Fourier transform infrared spectroscopy (FTIR) technique was applied in the early rapid detection of Plasmodiophora brassicae in root of Chinese cabbage while the symptom had not appeared. The Chinese cabbage root was inoculated with Plasmodiophora brassicae. Chinese cabbage root infected with Plasnmodiophora brassicae and uninfected root samples showed their difference in FTIR spectra. The absorption peaks at 1 227, 1 143 and 1 105 cm-1 were only found in the infected root samples, and combined with the variation in the peak area at these absorption peaks they could be used for early rapid detection for clubroot of Chinese cabbage. In addition, the polymerase chain reaction was used to verify the veracity of Fourier transform infrared spectroscopy (FTIR) technique. The results show that the detection results are consistent with each other, and they could detect the Plasmodiophora brassicae 5 days after inoculation. Results clearly demonstrated that the PTIR technology is a highly sensitive, convenient and quick one for the early rapid detection of clubroot of Chinese cabbage, and provides a new thought and method for the early detection of plant disease.