The utility model discloses a rounded-needle head injection syringe with a cannula. The rounded-needle head injection syringe with the cannula comprises a needle cylinder, a push bar arranged in the needle cylinder, a needle head mounting seat arranged at the front end of the needle cylinder and a needle head mounted on the needle head mounting seat. The front end of the needle head is semicircular, a first end portion syringe port is formed in the front end of the needle head, a first side portion syringe port is formed in the side wall of the front end of the needle head, a syringe cannula is sleeved on the external of the needle head, the upper end of the syringe cannula is buckled with the needle head mounting seat, the front end of the syringe cannula is semicircular, a second end portion syringe port is formed in the front end of the syringe cannula, the center of the second end portion syringe port and the center of the first end portion syringe port are disposed in the same straight line, a second side portion syringe port is formed in the side wall of the front end of the syringe cannula, and the second side portion syringe port and the first side portion syringe port are disposed on the same circumference. The rounded-needle head injection syringe with the cannula is simple in structure, reasonable in design, easy to operate and good in using effect, can be inserted into a blood vessel or a drainage tube along a tube wall smoothly without hurting the blood vessel or various drainage tubes, and can be adjusted according to the requirement of a syringe range.