Due to the influence of inherent characteristics of material, the bias operating point of electro-optic modulator may drift with changes in environment, thereby affecting the modulation performance of the modulator. To solve the bias point drift issue of lithium niobate Mach-Zehnder electro-optic modulators, bias control techniques suitable for 4-array parallel electro-optic modulators is researched. Based on time division multiplexing, adjustable gain amplitude, dual pattern recognition, and other methods, a control method combining optical power and disturbance signal amplitude detection is proposed, which reduces hardware redundancy and achieves precise control of the bias operating point.