The invention provides an unpowered rainfall runoff pollutant intercepting facility and a pollutant intercepting operation method. A facility main body is barrel-shaped in the whole, a water inlet pipe and a water outlet pipe are mounted at two sides of the upper part of the facility main body, respectively, the water inlet pipe is inserted into the facility main body in the form of an inclination angle and is connected with the circumferential tangent insertion inner wall of the facility main body, a flow guide barrel is mounted on a support frame in the facility main body, rainwater forms the vortex state between the inner wall of the facility main body and the flow guide barrel, then centrifugal force is generated, sundries in the rainwater fall into a sediment collecting area from a lower leaking hole of a flow guide plate, then a deslagging hole is opened, and the sundries are discharged. The unpowered rainfall runoff pollutant intercepting facility is simple in structure, good in reliability, and simple and convenient to mount and maintain, through the improvement on the original initial rainwater pollutant intercepting facility, the intercepting and processing efficacies for the rainfall runoff pollutants are improved, the improved facility main body is integrated, and is convenient to mount and overhaul, and only regular checking, desilting and pollutant discharge are needed.