The aim of this study is to evaluate the effect of Tizanidin on reducing bleeding during endoscopic sinus surgery that is a double blind study on control and test group.The patients are older than 16 years with ASA class I and II, and nasal polyposis that admitted to the Ghaem hospital and without cardiovascular system pathology, hypertension, liver or kidney disease, hemoglobin below 10 ,have coagulation disorders .Patients were randomly divided into two groups of 25, a control group that recieve placebo and the other group will be recieved 4 mg tizanidine with 50 cc of water, one hour before surgery .After entering patients into the operating room,head up position at 10 degrees,preparation and pre-oxygenation in patients initially for midazolam premedication and Fentanyl injection and then with propofol and Atracuriom induction of anesthesia is given. After 5 minutes the patients will be intubated . During surgery vital signs, including blood pressure measurement, ECG, heart rate, pulse oximetry ,capnography and BIS are controlled.Systolic and diastolic and mean arterial blood pressure with heart rate are recorded after induction, after intubation, after drug administration and every 5 minutes (half an hour) and then every 10 minutes until the end of the surgery. We evaluate surgeon satisfaction and the amount of bleeding based on the criteria of Boezarrt and Likertt . 3 minutes before the end of surgery anesthetic drugs will been reduced, after the complete return of muscle strength and injection reverse , patients will be extubated and transferred to recovery, and after the acquisition criteria of discharge will be transferred to the ward.