According to identity theory, individual identity consists of four dimensions: nature identity, institutional identity, discourse identity and affinity identity. Teachers’ nature identity refers to their biological characteristics; teachers’ institutional identity refers to their social status; teachers’ discourse identity refers to their teaching achievements; and teachers’ affinity identity refers to their cooperating state. From the perspective of identity theory, the nature identity of the non-staff teachers is divided and they are regarded as “one-dimensional man.” Their institutional identity is undecided and they are regard as “rootless people” in the school. Their discourse identity is fading away and they are regarded as “low-level” in school teaching. Their affinity identity is concealed and they are regarded as “outsiders” in the school. To improve the professional contentment of non-staff teachers and promote their high-quality development, it is necessary to care about their life world and respect their nature identity; protect their legitimate rights and interests and improve their institutional identity; highlight their professional strength and enhance their discourse identity; and make the “teacher community” play its role and intensify their affinity identity.