The invention relates to a controllable fully-degradable macromolecular material-based composite material and a preparation method thereof. According to the controllable fully-degradable macromolecular material-based composite material, a degradable macromolecular material serves as a matrix; magnesium oxide, magnesium hydroxide or a mixture of magnesium oxide and magnesium hydroxide serves as an enhanced phase; and the adding amount of the magnesium oxide, magnesium hydroxide or the mixture of magnesium oxide and magnesium hydroxide accounts for 0.5-40wt% of the composite material. The controllable fully-degradable macromolecular material-based composite material has the characteristics of high biosecurity, good degradation controllability, low material cost and the like, and has a wide application prospect in the technical field of manufacturing or surface modification of medicine controlled release carriers (such as medicinal capsules) and medical treatment appliance products, especially high-additional-value implants comprising 1) surgical sutures, 2) orthopedic internal fixation devices such as bone plates, bone nails, bone nets and the like, 3) artificial bone or bone repair materials, 4) intravascular stents, 5) tissue engineering stents and the like.