In the peripheral blood of patients with fever, it is generally easy to find the tropic spirochete. Gram staining of thin blood smear is negative, and Wright or Giemsa staining is red or purple. Under the dark field microscope, it can be seen that it moves forward or backward flexibly in the form of rotation and migration, and swings to both sides. Spirogyra can also be found in bone marrow smear. The culture medium must contain blood, ascites or kidney tissue, which can proliferate under the condition of micro-oxygen, but it is easy to decline and difficult to pass on.