Abstract: The present invention discloses a method for rapidly detecting the total nitrogen content of the soil in an urban green land by using archaea molecular marker OTU300. The present invention provides a DNA molecule (probe), as shown in SEQ ID NO. 1 of the sequence listing. The present invention also protects the application of the probe in detecting or assisting in detecting the total nitrogen content of the soil. The present invention also protects the application of the probe in comparing the total nitrogen content of the soil in different plots. Using the method provided by the present invention to detect the total nitrogen content of the soil or compare the total nitrogen content of the soil of different plots has the following advantages: small sample demand, no need for pre-treatment, short required time, low labor cost, and realizing the rapid automatic detection of large quantities of samples. The present invention deserves to apply and promote in the evaluation of soil samples.