A flat tube for a microchannel heat exchanger, comprising a first wallboard (1.1, 2.1, 3.1, 4.1) and a second wallboard (1.2, 2.2, 3.2, 4.2) that are formed separately, wherein the first wallboard (1.1, 2.1, 3.1, 4.1) is connected to the second wallboard (1.2, 2.2, 3.2, 4.2) to form a refrigerant circulation cavity, the first wallboard (1.1, 2.1, 3.1, 4.1) has a plurality of protrusion portions protruding into the refrigerant circulation cavity to form multiple refrigerant channels, arranged along a length direction of the flat tube, in the refrigerant circulation cavity; or the second wallboard (1.2, 2.2, 3.2, 4.2) has a plurality of protrusion portions protruding into the refrigerant circulation cavity to form multiple refrigerant channels, arranged along a length direction of the flat tube, in the refrigerant circulation cavity; or the first wallboard (1.1, 2.1, 3.1, 4.1) and the second wallboard (1.2, 2.2, 3.2, 4.2) both have a plurality of protrusion portions protruding into the refrigerant circulation cavity to form multiple refrigerant channels, arranged along a length direction of the flat tube, in the refrigerant circulation cavity; each of the plurality of protrusion portions of the first wallboard (1.1, 2.1, 3.1, 4.1) is a the first protrusion, each of the plurality of protrusion portions of the second wallboard (1.2, 2.2, 3.2, 4.2) is a second protrusion, characterized in that there are multiple first protrusions (1.3,3.3) and multiple second protrusions (1.4,3.4), any of three adjacent first protrusions (1.3,3.3) of the multiple first protrusions (1.3,3.3) on the first wallboard (1.1, 2.1, 3.1, 4.1) or any of three adjacent second protrusions (1.4,3.4) of the multiple second protrusions (1.4,3.4) on the second wallboard (1.2, 2.2, 3.2, 4.2) form an included angle θ = 2 arctan Lv Lh along a refrigerant flowing direction, where the Lv is a distance between two adjacent first protrusions (1.3,3.3) of the multiple first protrusions (1.3,3.3) along a width direction of the first wallboard (1.1, 2.1, 3.1, 4.1) or two adjacent second protrusions (1.4,3.4) of the multiple second protrusions (1.4,3.4) along a width direction of the second wallboard (1.2, 2.2, 3.2, 4.2), and the Lh is a distance between the two adjacent first protrusions (1.3,3.3) along a length direction of the first wallboard (1.1, 2.1, 3.1, 4.1) or the two adjacent second protrusions (1.4,3.4) along a length direction of the second wallboard (1.2, 2.2, 3.2, 4.2). the first wallboard (1.1, 2.1, 3.1, 4.1) has a plurality of protrusion portions protruding into the refrigerant circulation cavity to form multiple refrigerant channels, arranged along a length direction of the flat tube, in the refrigerant circulation cavity; or the second wallboard (1.2, 2.2, 3.2, 4.2) has a plurality of protrusion portions protruding into the refrigerant circulation cavity to form multiple refrigerant channels, arranged along a length direction of the flat tube, in the refrigerant circulation cavity; or the first wallboard (1.1, 2.1, 3.1, 4.1) and the second wallboard (1.2, 2.2, 3.2, 4.2) both have a plurality of protrusion portions protruding into the refrigerant circulation cavity to form multiple refrigerant channels, arranged along a length direction of the flat tube, in the refrigerant circulation cavity; each of the plurality of protrusion portions of the first wallboard (1.1, 2.1, 3.1, 4.1) is a the first protrusion, each of the plurality of protrusion portions of the second wallboard (1.2, 2.2, 3.2, 4.2) is a second protrusion, characterized in that there are multiple first protrusions (1.3,3.3) and multiple second protrusions (1.4,3.4), any of three adjacent first protrusions (1.3,3.3) of the multiple first protrusions (1.3,3.3) on the first wallboard (1.1, 2.1, 3.1, 4.1) or any of three adjacent second protrusions (1.4,3.4) of the multiple second protrusions (1.4,3.4) on the second wallboard (1.2, 2.2, 3.2, 4.2) form an included angle θ = 2 arctan Lv Lh along a refrigerant flowing direction, where the Lv is a distance between two adjacent first protrusions (1.3,3.3) of the multiple first protrusions (1.3,3.3) along a width direction of the first wallboard (1.1, 2.1, 3.1, 4.1) or two adjacent second protrusions (1.4,3.4) of the multiple second protrusions (1.4,3.4) along a width direction of the second wallboard (1.2, 2.2, 3.2, 4.2), and the Lh is a distance between the two adjacent first protrusions (1.3,3.3) along a length direction of the first wallboard (1.1, 2.1, 3.1, 4.1) or the two adjacent second protrusions (1.4,3.4) along a length direction of the second wallboard (1.2, 2.2, 3.2, 4.2).