A bottom stop assembly of a zipper comprises a left stop part and a right stop part, wherein the outer side of the left stop part and the outer side of the right stop part are connected with a left zipper chain and a right zipper chain respectively. A right inserting groove and an annular hole are formed in the inner side of the right stop part and extend in the inner side direction, the annular hole is located in the front end of the right inserting groove and is straightly communicated with a groove hole of the right inserting groove, and the left stop part can be movably inserted into the groove hole of the right inserting groove and can be taken off from the side edge port of the right inserting groove. When the left stop part is inserted into the groove hole of the right inserting groove, the top end portion of the left stop part can be inserted into the annular hole. As the left stop part can be inserted into the groove hole of the right inserting groove, the left stop part can be vertically positioned; as the left stop part can be taken off from the side edge port, when the left stop part is withdrawn from the right inserting groove, the left stop part can be driven by the left zipper chain to rotate around the outer side wall of the annular hole to be capable of rotating out, and withdrawing is very convenient and fast. The bottom stop assembly has the characteristics and the advantages, thereby being capable of being applied to bottom stop assemblies of zippers.