The invention discloses a complete plant for regeneration of magnesium oxide and recovery of acid by means of magnesium sulfate and magnesium sulfite waste residues. The complete plant comprises a feeding machine, a Venturi mixer, a multistage cyclone material preheating device, a suspension roaster, a gas material separating device, a multistage cyclone material cooling device, an air feeder, a fuel nozzle, an absorption liquid concentration device, a waste gas dedusting device, an induced draft fan, a sulfur dioxide absorbing device, a desulfuration device, a desulfuration liquid lift pump, an absorption liquid lift pump and an acid storage tank. The complete plant comprises all factors involved with powdery material preparation, feeding and discharging, flash roasting, preheating utilization, waste gas treatment and other production processes. Product activity is high, granularity is small, quality is high, and value is high; the utilization rate of waste heat is high, efficiency is high, effect is good, and waste gas outlet temperature and discharging temperature are both under 120 DEG C; energy consumption is low, material waste heat and hot waste gas waste heat are fully utilized, and energy consumption is reduced greatly; production is conducted in an environment-friendly and closed mode, and waste gas is discharged after being treated to meet standards; production technology is advanced, production efficiency is high, effect is good, operation is stable, and operation is convenient.