A drip irrigation emitter has an outer element and a flow-restricting element. The outer element has a channel, an inlet and an outlet. The flow-restricting element is detachably mounted in the channel of the outer element. The flow-restricting element has a body, a passageway, a piercing portion and multiple notches. The passageway is helically formed around the body and has a caliber. The piercing portion is mounted on the body and protrudes out of the inlet. The notches are formed around the body between a first end surface of the body and the piercing portion and are in communication with the passageway. Each one of the notches has a caliber that is smaller than the caliber of the passageway to prevent the passageway from obstruction by the impurities. The piercing portion can directly pierce into a water supply tube for adjusting to plants accurately.
