The invention relates to a magnesium matrix microarc oxidation electrolyte liquid and a microarc oxidation method thereof. The electrolyte liquid comprises: 3 - 40g / L of fluozicronate, 0.5 - 10 g / L of oxalate, 2 - 20 g / L of phosphoric acid, 1 - 20 g / L of acetate, 3 - 30 g / L of phosphate, 0.5 - 10 g / L of fluoride. The operation method is that: a magnesium workpiece is taken as anode, stainless steel is taken as cathode, a pulse power supply is adopted, constant voltage is 350 - 650V, frequency is 50 - 2000Hz, duty ratio is 10 - 40 percent, and the electrolyte liquid is oxidated through microarc under the condition that the distance between a cathode plate and an anode plate is 8 - 12 cm, the temperature of the electrolyte liquid is kept for 10 - 40 DEG C with the treatment time of 5 - 90min. the electrolyte liquid of the invention does not comprise Cr6+, thus having not too large pollution to environment; the obtained film layers which consists of anti-corrosive substances have the advantages of smooth surface, ceramics appearance, strong combination, comparatively larger thickness, high density and little pores, high hardness, etc.