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The special operation mode of high-speed railway will generate a large amount of harmonics. The harmonics will be transmitted to the 220kV side high-voltage cables through the traction transformer, and harmonic voltages will be generated on the cable sheath, threatening the safe operation of the cables. In this paper, on the basis of the measured harmonic data of the traction substation, a harmonic source model based on the measured data is established, which solves the complex problem of harmonic source modeling and can accurately reflect the actual operating conditions of high-speed trains. On this basis, the harmonic voltage characteristics of the cable sheath on the 220kV side of the high-speed railway under the three working conditions of traction, regenerative braking and inertia are simulated and calculated, and the effects of cable length, cable grounding method, and harmonic current parameters on the harmonic voltage are explored. Affect the law. The results show that under different operation modes of high-speed rail, the harmonic voltage of the sheath far exceeds the normal operation of the power frequency, and the maximum value of the harmonic voltage of the cable sheath can reach 454V under the traction condition; Under working conditions, the overvoltage of the metal sheath is greatly affected by the grounding method of the cable, the length of the cable and the harmonic current content. The above research results have important reference significance for the safe operation of electrified railways.