This paper proposes a novel photonic crystal optical fiber which can support 30 orbital angular momentum (OAM) modes transmission and possesses relatively flat and low dispersion. The OAM modes can be well-separated due to the large effective refractive index difference (above 10^-4) between the eigenmodes. The only material of the designed fiber is silica. The dispersion of each OAM mode is controlled in the range of 50—100 ps·nm^-1·km^-1 and the total dispersion variation is below 10 ps·nm^-1·km^-1 from 1 500 nm to 1 600 nm. Moreover, the confinement loss of each OAM mode is below 8.17×10^-10 dB/m at 1 550 nm, and the nonlinear coefficients is less than 0.71 W^-1/km for all modes at 1 550 nm. With all these good features, this proposed optical fiber is promising to be applied in fiberbased OAM communication systems.