The invention provides a medical implanted degradable composite bar and a preparing method thereof. The medical implanted degradable composite bar is characterized in that the innermost layer is a magnesium alloy, the middle layer is a zinc alloy, the zinc alloy and the magnesium alloy are connected in the form of a dovetail groove, the liquid zinc alloy is poured around the solid magnesium alloyat the high temperature, so that the magnesium alloy and the zinc alloy are in metallurgical bonding, and the outermost layer is a biological coating. The magnesium alloy comprises chemical componentsincluding, by mass percent, 8%-15% of CaO, 3%-10% of Zn, 2%-8% of Sr, 0.8%-2% of Ce and the balance Mg. The zinc alloy comprises chemical components including, by mass percent, 0.1%-1.0% of Mg, 0.5%-2.0% of Mn, 0.05%-0.6% of Sr, 0.1%-0.5% of Sn, 0.08%-0.6% of La and the balance Zn. The biological coating comprises chemical components including, by mass percent, 50%-65% of nano beta-Ca3(PO4)2 andnano CaCO3 composite particles, 3%-8% of nano silver particles and the balance polylactic acid, wherein the mass ratio of nano beta-Ca3(PO4)2 to nano CaCO3 is 1:2. The composite bar has good mechanical performance, the medical requirements can be met, integral materials can be completely degraded, and taking-out through the second operation is not needed.