A novel microstructured optical fiber is proposed and can support the transmission of 22 orbital angular momentum (OAM) modes, which has the advantages of flat and low dispersion and low loss. The OAM modes can be well-separated due to the large effective refractive index difference (above 10 -4) between the eigenmodes corresponding to each OAM mode. In the range of 1500-1600 nm, By adjusting the diameters of the first two inner rings of air-holes, we can controll the dispersion of each mode in the range from 0 to 50 ps·(nm·km) -1. The dispersion variations of HE71 and EH51 modes are less than 12.8 ps·(nm·km) -1, and the dispersion variations of other modes are less than 5 ps·(nm·km) -1. Moreover, this fiber possesses a very low confinement loss below 1.35×10 -9 dB/m for all the supported modes at 1550 nm.