The invention provides a biodegradable plastic cement material and a preparation method thereof. The material comprises polylactic acid, polymethyl methacrylate, polypropylene, dicapryl phthalate, butyl benzyl phthalate, castor oil, cocoanut fatty acid diethanolamide, cellulose, modified starch, butylated hydroxytoluene, butyl hydroxy anisd, polymethyl acrylate and silica. The preparation method comprises the steps of firstly, mixing, heating and stirring polylactic acid, polymethyl methacrylate, polypropylene, dicapryl phthalate, butyl benzyl phthalate, castor oil and cocoanut fatty acid diethanolamide, then adding the remaining components, conducting dispersion, then placing the mixture into a dryer for a reaction, and finally adding the mixture into a double-screw extruder for extrusion molding. The biodegradable plastic cement material can be degraded completely, is high in degradation speed and meanwhile has quite good elasticity and toughness.