An improved composite cup structure comprising: an inner plastic cup (1) and an outer paper cup (2). The composite cup is manufactured from paper and plastics by a ratio of 7:3. The rims of both inner plastic cup (1) and outer paper cup (2) are provided with outwards curled edges (11, 21). The curled edge (11) of the inner plastic cup (1) is slightly larger than that of the outer paper cup, and a flat surface (F) is formed on the top. An extension member (12) is formed on the curled edge of the inner cup. The extension member (12) contributes to the separation of inner and outer cups (1, 2) for classification and recycling.