A method for mounting an inner support beam of a container, comprising fixing a bottom support beam and a back support beam to a container body in a reusable and detachable manner; positioning the bottom support beam on a floor of the container body, and supporting the back support beam on a side wall corrugated plate of the container body, wherein the bottom support beam is a channel steel having a pair of sides consisting of a front side wall and a rear side wall with exterior surfaces and opposite ends, wherein at least one of the opposite ends of the bottom support beam is provided with a first clamping lug group, the first clamping lug group comprises two first clamping lugs respectively arranged on the front side wall and the rear side wall of the bottom support beam, there is a certain distance between the first clamping lugs and an end surface of the at least one of the opposite ends of the bottom support beam; the back support beam includes a main beam which is a channel steel having a pair of sides with exterior surfaces, a top end and a bottom end, wherein the bottom end of the main beam of the back support beam is provided with two second clamping lugs spaced apart and extending downward, a space between the two second clamping lugs forms a clamping groove, the clamping groove is clamped on the at least one of the opposite ends of the bottom support beam, and each second clamping lug is located between corresponding first clamping lug and the side wall corrugated plate, such that each first clamping lug restricts a displacement of corresponding second clamping lug in an extending direction of the bottom support beam, so that the bottom support beam and the back support beam are in an interlocked state, the back support beam further comprises a plurality of support members connected behind the main beam, the plurality of support members are arranged along an extending direction of the main beam; wherein the back support beam is supported in a groove of the side wall corrugated plate; the top end of the main beam of the back support beam is connected to the side wall corrugated plate in a reusable and detachable manner, the at least one of the opposite ends of the bottom support beam is jointed to the bottom end of the main beam the back support beam in a reusable and detachable manner and in a manner of at least restricting movement of the bottom end of the main beam of the back support beam in a direction away from the side wall corrugated plate; the main beam faces an interior of the container body and; the main beam is vertically arranged or is obliquely arranged along a direction from the bottom end of the main beam to the top end of the main beam toward a direction close to the side wall corrugated plate; the plurality of support members are supported in the groove of the side wall corrugated plate. the bottom support beam is a channel steel having a pair of sides consisting of a front side wall and a rear side wall with exterior surfaces and opposite ends, wherein at least one of the opposite ends of the bottom support beam is provided with a first clamping lug group, the first clamping lug group comprises two first clamping lugs respectively arranged on the front side wall and the rear side wall of the bottom support beam, there is a certain distance between the first clamping lugs and an end surface of the at least one of the opposite ends of the bottom support beam; the back support beam includes a main beam which is a channel steel having a pair of sides with exterior surfaces, a top end and a bottom end, wherein the bottom end of the main beam of the back support beam is provided with two second clamping lugs spaced apart and extending downward, a space between the two second clamping lugs forms a clamping groove, the clamping groove is clamped on the at least one of the opposite ends of the bottom support beam, and each second clamping lug is located between corresponding first clamping lug and the side wall corrugated plate, such that each first clamping lug restricts a displacement of corresponding second clamping lug in an extending direction of the bottom support beam, so that the bottom support beam and the back support beam are in an interlocked state, the back support beam further comprises a plurality of support members connected behind the main beam, the plurality of support members are arranged along an extending direction of the main beam; wherein the back support beam is supported in a groove of the side wall corrugated plate; the top end of the main beam of the back support beam is connected to the side wall corrugated plate in a reusable and detachable manner, the at least one of the opposite ends of the bottom support beam is jointed to the bottom end of the main beam the back support beam in a reusable and detachable manner and in a manner of at least restricting movement of the bottom end of the main beam of the back support beam in a direction away from the side wall corrugated plate; the main beam faces an interior of the container body and; the main beam is vertically arranged or is obliquely arranged along a direction from the bottom end of the main beam to the top end of the main beam toward a direction close to the side wall corrugated plate; the plurality of support members are supported in the groove of the side wall corrugated plate.