Abstract: In order to get photonic crystal fiber with anomalous dispersion, which can be used as the gain part of a Yb³⁺-doped pulse fiber laser, a structure of photonic crystal fiber(PCF) with Yb³⁺-doped aluminosilicate glass core was designed. The cross-section of the core was oval, the cladding was the ordinary hexagonal structure with air holes in the same diameter, and there were four small air oval holes between the core and the cladding. The influences of air hole's diameter d, pitch Λ and the ratio d/Λ of the cladding on the relationship between dispersion and wavelength were studied, as well as the influence of four small air oval holes on the relationship between dispersion and birefringence. The results show that when Λ is 2.3μm and d/Λ is 0.5, the anomalous dispersion is observed, and this photonic crystal fiber can be used as the gain part of a Yb³⁺-doped pulse fiber laser as well. The research is helpful for the use of Yb³⁺-doped PCF as the gain part of a pulse fiber laser.