The invention relates to a synchronous sintering method of a titanium alloy or a pure titanium product in powder injection molding. The synchronous sintering method comprises the following steps: S1,an injection blank of the titanium alloy or pure titanium is prepared; S2, a sintering jig injection blank is prepared, wherein, A, powder is mixed, specifically, ceramic powder and a low-temperaturesintering aid are uniformly mixed; B, feed is prepared, specifically, the uniformly mixed powder is prepared into feed particles; and C, the feed particles are subjected to injection molding through an injection molding machine to obtain the sintering jig injection blank; S3, placing is conducted, specifically, the injection blank of the titanium alloy or the pure titanium is placed on the sintering jig injection blank; S4, catalyzing is conducted, specifically, a catalytic blank is obtained; S5, thermal desorption is conducted, specifically, a thermal desorption blank is obtained; and S6, sintering is conducted, specifically, a sintered blank is obtained. According to the synchronous sintering method of the titanium alloy or the pure titanium product in powder injection molding, the product and a sintering jig are synchronously sintered, thus synchronous shrinkage of the sintering jig and the product is achieved, the sintering jig has a good supporting effect on the product, and therefore sintering deformation of the titanium alloy or the pure titanium product is effectively improved, and the sintering yield is increased.