The invention discloses a diffusion connection method of a laminated composite material and low-alloy steel. The method mainly comprises the steps that a niobium foil intermediate alloy is added into the position between contact interfaces of the laminated composite material and the low-alloy steel, the laminated composite material and the low-alloy steel are subject to vacuum diffusion connection, according to the technological parameters, a step-by-step temperature rising manner is adopted, the positions at the temperature of 550 DEG C, 750 DEG C and 950 DEG C are each provided with a platform, the diffusion connection temperature ranges from 1020 DEG C to 1180 DEG C, heat preservation time ranges from 30 min to 80 min, connection pressure ranges from 5 MPa to 15 MPa, the vacuum degree ranges from 1.33*10<-5> Pa to 1.33*10<-4> Pa, and after the temperature of a vacuum chamber is slowly reduced to below 100 DEG C, a furnace door can be opened, and a connected part is taken out. According to the technology, the interface diffusion combination of the laminated composite material and the low-alloy steel can be promoted, the strength and the mechanical property of a connection joint are stable and reliable, and the technology can meet the use requirement of a laminated composite material and low-alloy steel diffusion joint.