The invention provides a preparation method of a positive electrode material for a lithium-sulfur battery. The method comprises the steps of: (A) carrying out carbonization treatment on nut shells, carrying out activating treatment on the obtained carbonized material and an alkali compound in a solvent to obtain an activated porous carbon material; (B) carrying out acid treatment on the activated porous carbon material to obtain the oxidized activated porous carbon material; and (C) mixing the oxidized activated porous carbon material with sublimed sulfur to obtain the positive electrode material for the lithium-sulfur battery. The preparation method is simple, feasible, environment-friendly and beneficial to industrial production. The lithium-sulfur battery prepared from the positive electrode material has relatively high specific discharge capacity, cycle performance and rate capability. An experiment shows that the initial specific discharge capacity of the lithium-sulfur battery at the rate of 0.1C is 1024.41mAh/g-1261.52mAh/g; the specific discharge capacity is 429.62mAh/g-586.95mAh/g after 50 charging and discharging cycles; and the coulombic efficiency is close to 100%.