The invention discloses an ultrathin single crystal germanium wafer processing method. The ultrathin single crystal germanium wafer processing method is characterized by comprising the following steps: first, using wire-electrode cutting equipment to cut a single crystal germanium rod to obtain single crystal germanium wafers with the thickness being less than 0.5mm; second, clamping the single crystal germanium wafers on a low-temperature polishing machine; third, firstly using a hard abrasive material with the Mohs hardness being greater than 9, such as diamond, corundum, silicon carbide, boron carbide with the granularity of 10-28[mu]m to froze and solidify an abrasive material polishing disk to serve as a polishing head for rough machining, and taking an anhydrous organic solvent as polishing liquid; using an abrasive material with the Mohs hardness being smaller than 9, such as CeO2 and silica with the granularity of 0.06-2[mu]m to froze and solidify the abrasive material polishing disk to serve as a polishing head for fine machining, and carrying out secondary processing, wherein the polishing temperature is controlled to be within minus 30DEG C to minus 10DEG C, the polishing pressure is controlled to be within 100-500g / cm<2>, the polishing solution is the anhydrous organic solvent, the flow rate is 50-500ml / min, the polishing rotation speed is 10-300r / min, and finally the ultrathin germanium wafers with the thickness being less than 0.15mm are obtained. The ultrathin single crystal germanium wafer processing method is simple and the yield is high.