Based on the full-vector finite element method, a novel structure of highly negative dispersion photonic crystal fiber with the central index dip in the low germanium doped core is proposed. The highly negative dispersion can be obtained at the wavelength of 1.55 m by adjusting the pitch, the air-hole diameter in the third ring, the germanium doped concentration and the influence of central index dip. This work has been supported by the National Natural Science Foundation of China (Grant No.60877033) and Key Program of Education Ministry of China (Grant No.308002)