The invention discloses a magnesium oxide composite floor and a manufacturing process thereof. The floor sequentially comprises a surface wear-resistant layer, a surface slurry layer, an upper glass fiber gridding cloth layer, an upper glass fiber short fiber felt layer, a main body material layer, a lower glass fiber short fiber felt layer, a lower glass fiber gridding cloth layer, a bottom slurry layer and a bottom wear-resistant layer from top to bottom, wherein the main body material layer contains magnesium oxide, a magnesium chloride solution, heavy calcium powder, powder and a modifier;the surface slurry layer contains magnesium oxide, a magnesium chloride solution, fossil powder, powder and a modifier; and the bottom slurry layer contains magnesium oxide, a magnesium chloride solution, fossil powder, powder and a modifier. The floor is simple in structure, the manufacturing process is simple and feasible, and the manufactured floor is good in fireproof, moisture-proof and water-resistant properties, high in strength and not easy to deform.