The invention discloses a powder metallurgy process. The powder metallurgy process comprises the following steps that 1), molding is conducted, wherein a warm-pressing lubricant is added to iron-based powder, mixed and then put into a molding die at the die temperature of 100 DEG C to 120 DEG C and is subjected to die-casting molding through a press till the density of a workblank obtained through die-casting is larger than or equal to 7.35 g/m<3>; 2), primary sintering is conducted, wherein under the nitrogen-hydrogen sintering atmosphere protection effect, high-temperature sintering is conducted at the temperature of 1,120 DEG C to 1,150 DEG C for 35 minutes to 40 minutes; 3), shaping is conducted, wherein shaping is conducted on the workblank obtained after primary sintering is conducted through a machining manner, and a primary sintered product is obtained; 4), secondary sintering is conducted, the primary sintered product is subjected to high-temperature sintering at the temperature of 1,180 DEG C to 1,200 DEG C for 30 min to 35 min under the nitrogen-hydrogen sintering atmosphere protection effect, and a secondary sintered product with the density being larger than or equal to 7.4 g/cm<3> is obtained; and 5), post-treatment is conducted, the secondary sintered product is subjected to a washing working procedure, and a finished product is obtained. The invention further discloses a car model differential gear produced through the powder metallurgy process.