The invention discloses a biodegradable Mg-Ca-Mn-Sn magnesium alloy material and a preparation method and application thereof. The biodegradable Mg-Ca-Mn-Sn magnesium alloy material is prepared from the following components, by mass percentage, 0.5-3% of Ca, 0.1-2% of Mn, 1-5% of Sn and the balance Mg and inevitable impurity elements brought in by raw materials. The specific preparation method includes smelting of the raw materials, casting molding, uniform annealing treatment and hot extrusion processing. The biodegradable Mg-Ca-Mn-Sn magnesium alloy has no any toxicity on human bodies and is good in mechanical performance, the preparation method is simple and low in cost, plate-shaped and rod-shaped materials in different size and cross section requirements can be prepared as required, and the biodegradable Mg-Ca-Mn-Sn magnesium alloy material can be used for preparation of bone lamellae, bone nails and other orthopedic implants, cardiovascular stents and other medical materials.