The invention discloses a double-fuel fuel injector. The double-fuel fuel injector comprises a shell body, a main valve core, a first fuel channel, a second fuel channel, an auxiliary valve core and a rotating trough, wherein the main valve core is arranged in the shell body and can move in the axial direction of the shell body, a ring-shaped pressure storing cavity is defined by the main valve core and the bottom of the shell body, the first fuel channel is arranged in the center of the interior of the main valve core, the upper end face of the first fuel channel is bent towards the shell body, the lower end of the first fuel channel is gradually contracted to form a throat pipe, the lower end of the throat pipe forms a diffusion cavity, first nozzles are evenly formed in the lower end of the diffusion cavity, the second fuel channel is arranged the lower end, close to the shell body, of the interior of the main valve core and communicates with the ring-shaped pressure storing cavity, the auxiliary valve core is arranged in the bent position on the upper portion of the first fuel channel in the main valve core and can move in the radial direction of the shell body, the periphery of the rotating trough is arranged on the inner wall of the lower end of the shell body, and the rotating trough communicates with the throat pipe. The double-fuel fuel injector can be installed on a cylinder cover of an engine in integration and intensification modes, and single-fuel injecting, double-fuel mixed injecting and double-fuel independent injecting are conducted.