The invention provides a connector for being connected between a wiper arm and a wiper piece of the windscreen wiper system. The wiper arm comprises an insertion space and an opening communicated with the insertion space. The wiper piece comprises an adaptor. The connector comprises a body which can be installed on the adaptor and can be inserted into the insertion space in the insertion direction, and a connecting portion which extends out of the body and can elastically deform to the release position under the action of external force and reduce elastic deformation to the blocking position when the external force is removed. When the connecting portion is located at the release position, the body and the connecting portion can freely move in the insertion space; when the connecting portion is located at the blocking position, the connecting portion can enter the opening to prevent the body from moving in the insertion space. The invention further provides a wiper piece assembly with the connector, and a windscreen wiper system with the wiper piece assembly.