The invention discloses an intelligent flue gas cleaning system capable of achieving online maintenance. The problems that in the prior art, energy resources are wasted, the flue gas cleaning efficiency is low, the flue gas cleaning schedule is delayed after a flue gas cleaning tower breaks down, and the automatic degree is low are solved. The intelligent flue gas cleaning system comprises a heatexchanger, and the flue gas cleaning tower, a control cabinet and a flue gas conveying pipe provided with a flue gas flowing sensor; the heat exchanger comprises a heat exchanger shell, an S-shaped heat exchange pipe, a hot water outlet pipe, a cold water inlet pipe, a temperature sensor and a water flow adjusting valve; the flue gas cleaning tower comprises a flue gas cleaning tower body, a fluegas cleaning alkali water pool, a spraying device and an exhaust window, the cleaning alkali water pool is provided with a flue gas pipe, a pollution discharge water pipe and an alkali water inlet pipe, and the spraying device comprises a spraying pipe, an alkali water conveying pipe, a high pressure water conveying pump and a spraying head; and the control cabinet is provided with a microprocessor and a liquid crystal control panel. The intelligent flue gas cleaning system is simple in structure, energy conservation and environmental protection are achieved, the flue gas cleaning efficiency is high, the cleaning effect is ideal, the flue gas cleaning tower can be maintained online to guarantee the flue gas cleaning schedule, and the automatic degree is high.