The invention discloses an Mg-Si-Ca-Zn series magnesium alloy and preparation method and application thereof. The magnesium alloy comprises Mg-Si-Ca-Zn, the mass percentage of Si in the magnesium alloy is 0-1.0% without being 0, the mass percentage of Ca is 0-1.0% without being 0, and the mass percentage of Zn is 2.0-3.0%, without being 0. The magnesium alloy further comprises trace elements, thetrace elements comprise at least one of strontium, manganese, phosphorus, zirconium, tin, iron, copper and rare earth elements, and the mass percentage of the trace elements is 0-3% without being 0. The mechanical strength of the Mg-Si-Ca-Zn series magnesium alloy conforms to the strength requirements of a medical implanted material, by adjusting and controlling the content of the added alloy elements, the adjustment and control of the degradation speed of the alloy elements in a humane body can be achieved, the experimental results show that the alloy elements has no obvious toxicity to osteoblast, the biocompatibility is high, the patient pain is reduced, and the postoperative safety and comfort are improved.