Co-current flow type hydrocracking method

The invention relates to a co-current flow type hydrocracking method. According to the method, fresh raw material oil is concurrently introduced to a hydrorefining reactor and a hydrocracking reactor in a co-current flow manner; the reaction effluent of the hydrorefining reactor is separated to obtain a light naphtha fraction, a heavy naphtha fraction, a middle fraction oil and a tail oil fraction; all or part of the tail oil fraction enters the hydrocracking reactor, and the reaction effluent of the hydrocracking reactor and part of the raw material oil enter the hydrorefining reactor. In the prior art, under an ammonia-free environment, cracking activity of a hydrocracking catalyst is too strong so as to cause secondary cracking of more middle fraction oil. With the method of the present invention, the problem in the prior art is prevented so as to effectively improve yield of the middle fraction oil. In addition, partial pressure of H2S is improved, and activity and selectivity of the sulfided hydrocracking catalyst are effectively protected.