The present disclosure provides a battery module, a busbar and a busbar assembly thereof. The busbar comprises a first connecting portion, a second connecting portion and a first main portion. The first connecting portion is connected to a first battery of the battery module, the second connecting portion is connected to a second battery. The first main portion connects the first connecting portion and the second connecting portion, and the first connecting portion and the second connecting portion are positioned at the same side of the first main portion in a transverse direction. The first connecting portion and the second connecting portion are spaced from each other in a longitudinal direction, and a first slit is formed between the first connecting portion and the second connecting portion. The first main portion is provided with a first notch, the first notch is communicated with the first slit.