Disclosed are a lead-free, high-sulphur and easy-cutting copper-manganese alloy and preparation method thereof. The alloy comprises the following components in percentage by weight: 52.0-95.0 wt. % of copper, 0.01-0.20 wt. % of phosphorus, 0.01-20 wt. % of tin, 0.55-7.0 wt. % of manganese, 0.191-1.0 wt. % of sulphur, one or more metals other than zinc that have an affinity to sulphur less than the affinity of manganese to sulphur, with the sum of the contents thereof no more than 2.0 wt. %, and the balance being zinc and inevitable impurities, wherein the metals other than zinc that have an affinity to sulphur less than the affinity of manganese to sulphur are nickel, iron, tungsten, cobalt, molybdenum, antimony, bismuth and niobium. The copper alloy is manufactured by a powder metallurgy method, in which after uniformly mixing the alloy powder, sulphide powder and nickel powder, pressing and shaping, sintering, re-pressing, and re-sintering are carried out to obtain the copper alloy, and the resulting copper alloy is thermally treated.