A busbar of a battery module, being an integral metal member in the shape of plate and comprising a first connecting portion, a second connecting portion and a first main portion; the first connecting portion being capable of being connected to a first battery of the battery module, the second connecting portion being capable of being connected to a second battery of the battery module; the first main portion connecting the first connecting portion and the second connecting portion, and the first connecting portion and the second connecting portion being positioned at the same side of the first main portion in a transverse direction; the first connecting portion and the second connecting portion being spaced from each other in a longitudinal direction, and a first slit being formed between the first connecting portion and the second connecting portion; the first main portion being provided with a first notch, the first notch being communicated with the first slit, wherein the first connecting portion has a first surface at a side close to the second connecting portion, the second connecting portion has a second surface at a side close to the first connecting portion, the first slit is positioned between the first surface and the second surface; the first main portion comprises a third surface, the third surface is provided along an edge of the first notch; the third surface comprises a first arc section, two ends of the first arc section are respectively connected with the first surface and the second surface; and the first surface and the second surface are planes and parallel with each other; characterized in that the third surface further comprises a second arc section and a third arc section; the second arc section connects the first surface and the first arc section, and the second arc section is inclined relative to the first surface toward a direction close to the second connecting portion; the third arc section connects the second surface and the first arc section, the third arc section is inclined relative to the second surface toward a direction away from the first connecting portion, and an arc length of the third arc section is less than an arc length of the second arc section. the first connecting portion being capable of being connected to a first battery of the battery module, the second connecting portion being capable of being connected to a second battery of the battery module; the first main portion connecting the first connecting portion and the second connecting portion, and the first connecting portion and the second connecting portion being positioned at the same side of the first main portion in a transverse direction; the first connecting portion and the second connecting portion being spaced from each other in a longitudinal direction, and a first slit being formed between the first connecting portion and the second connecting portion; the first main portion being provided with a first notch, the first notch being communicated with the first slit, wherein the first connecting portion has a first surface at a side close to the second connecting portion, the second connecting portion has a second surface at a side close to the first connecting portion, the first slit is positioned between the first surface and the second surface; the first main portion comprises a third surface, the third surface is provided along an edge of the first notch; the third surface comprises a first arc section, two ends of the first arc section are respectively connected with the first surface and the second surface; and the first surface and the second surface are planes and parallel with each other; characterized in that the third surface further comprises a second arc section and a third arc section; the second arc section connects the first surface and the first arc section, and the second arc section is inclined relative to the first surface toward a direction close to the second connecting portion; the third arc section connects the second surface and the first arc section, the third arc section is inclined relative to the second surface toward a direction away from the first connecting portion, and an arc length of the third arc section is less than an arc length of the second arc section.