The invention provides a method for preparing WC (wolfram carbide) powder by utilizing CH4 to reduce and carbonize WO3. The method effectively utilizes methane to directly reduce and carbonize WO3 nanopowder to obtain a WC powder product. The source of the methane gas is wide and the cost is low. Highly activated carbon and hydrogen of methane pyrolysis directly participate in reduction and carbonization reaction, WO3 can be reduced and carbonized under a low-temperature environment of 600 DEG C to 800 DEG C for 30 to 90 minutes, and thereby the WC powder product is prepared. The reduction and carbonization temperature is low, the time is short, the energy consumption and cost of production can be remarkably reduced, the method is used for implementing the large-scale low-cost industrial production of WC powder, moreover, the prepared WC powder has small average grain size, large specific surface area, good mechanical properties and good sphericity, the requirement of industrial application can be effectively met, and the WC powder can be used for preparing high-performance ultrafine-grain hard cemented carbide and highly activated wolfram carbide catalyst.