(I) Principle: BCG induces a non-specific immune response that elicits a Thl cell-mediated immune response and anti-tumor activity, thereby reducing the risk of tumor progression and recurrence. (ii) Usage: BCG has no significant benefit by single infusion, so long-term maintenance infusion is required. Currently, the usual dosage of BCG in China is 60~120 mg, dissolved in 40~50 ml of saline. It should be administered once a week for 6 weeks; subsequently, it can be maintained once every 2 weeks. (C) Perfusion process 1. Preparation before perfusion: (1) Tuberculin skin test: confirm non-strong positive (suggesting non-tuberculosis active stage). (2) Urine should be emptied before bladder perfusion and confirm that no large amount of water, fluids and diuretics (such as hydrochlorothiazide and other drugs) have been taken within the last 2 hours. 2. During perfusion: Keep the body relaxed during perfusion so that the urethral muscles are relaxed to facilitate smooth entry of the catheter into the bladder. Patients with conditions such as urethral stricture can explain to the outpatient doctor in advance so that the appropriate size catheter can be replaced. 3. After instillation: lie flat and change positions appropriately, keeping a total of 2 hours, during which the positions are changed (30 minutes each for supine, left lateral, right lateral and prone positions in that order), and the time can be shortened appropriately for patients with urinary frequency and urgency and small bladder. If the patient has a history of urinary retention, it is recommended to retain the urinary catheter after instillation of BCG until the BCG instillation fluid is drained and then remove it. Encourage drinking more water for 1 week after urination to expel the residual drug from the body, and avoid tea, coffee, alcohol and cola drinks during this period to reduce bladder irritation. 4. Fluoroquinolones, macrolides, tetracyclines, and aminoglycoside antibiotics are prohibited during irrigation because the above drugs can reduce the efficacy of BCG. （The following adverse reactions may occur after BCG instillation: cystitis, dyspareunia, hematuria, flu-like symptoms, fever, night sweats, pneumonia, malaise, arthralgia, granulomatous prostatitis, epididymitis, decreased bladder capacity, reactive lymph node enlargement, and sepsis caused by BCG. Therefore, it is encouraged to drink plenty of water after urination by perfusion to expel the residual drug from the body. Special attention is paid to the fact that the first urine discharge after perfusion contains a large amount of chemical drugs, so it is recommended that the first urine discharge be performed in the hospital. The treatment of urine within 6 h after treatment should be noted: after urination, pour an appropriate amount of bleach solution into the toilet and keep it for 15-20 minutes before flushing the toilet. Wish you a happy life and a speedy recovery!