A thread structure for an aerator of a water faucet outlet, wherein an internal and/or external thread structure of the aerator enables the aerator to be engaged with both metric and imperial internal threads on the water faucet outlet, wherein the dimensions of the structure is based on the pitch, the major diameter and the pitch diameter of the metric and imperial thread of the water faucet outlet and the variation tolerance, and wherein calculations are made based on the universal measurement of corresponding pitch, major diameter and, pitch diameter and the variation tolerance, such that the aerator can be engaged and locked in a metric faucet water outlet and also can be engaged and locked in an imperial faucet water outlet, thereby achieving a universal utilization effect.