The effects of turbulence aberrations on Orbital Angular Momentum (OAM)-multiplexed system by numerical simulation were analysed, where the turbulence aberration was simulated by several random phase screens generated by Kolmogorov model. The performances of normalized-received power and Bit Error Rate(BER) of the OAM-multiplexed system were characterized through changing the refractive index structure constant C2n and transmission distance z. The results show that normalized-received power decreases and the BER performance increases while the constant C2n and transmission distance z increases. The normalized-received power decreases to less than 0.2 and BER increases to more than 0.3 when the refractive index structure constant C2n is 5×10－13m－2/3. The normalized-received power decreases to less than 0.3 and BER increases to more than 0.35 while transmission distance z reaches 10 000 m. The comparison of the BER performance between two OAM-multiplexed systems with different values of the azimuthal index l is characterized. The results show that the OAM-multiplexed system which has closer values of l is more affected by atmospheric turbulence. At last, the BER with atmospheric tarbulence is decreased by two to three orders of magnitude compared with that one without atmospheric tarbulence at the same OSNR. The researchs have a good reference value for practical application of OAM-multiplexed system.