In order to reduce the loss of communication system based on orbital angular momentum (OAM), an Er3+-doped photonic crystal fiber (PCF) amplifier which can support amplification for 30 OAM modes is proposed. The structure of the PCF is optimized to obtain larger effective mode field area and effective refractive index difference. Then, the optimal PCF with a nonlinear coefficient lower than 0.002 m−1·W−1 is proposed, and it is used to setup an orbital angular momentum erbium-doped fiber amplifier (OAM-EDFA). Finally, an OAM-EDFA with a flat-high gain of about 28 dB, a DMG lower than 0.18 dB, and a NF no more than 4.4 dB is obtained. Compared with the existing OAM-EDFA, the gain of the proposed OAM-EDFA is increased by 6 dB. The OAM-EDFA based on the novel PCF designed in this work is of great interest to the OAM-based long-distance communication system.