Abstract: A bead chain safety system for roller blinds is revealed. The system includes a fixing base, an assembly base, a rotary disc, a first transmission member, and an elastic member. When a child entangled pulls a bead chain, the first transmission member is retracted into a cavity of the rotary disc and both the rotary disc and the bead chain are released from a rotary-disc mounting space between the fixing base and the assembly base. In order to put the rotary disc and other parts back, first the elastic member and the first transmission member are mounted into the cavity in turn. Then the rotary disc and the bead chain are set into the rotary-disc mounting space. The first transmission member pushed back by the elastic member is locked with and positioned by a second transmission member. Thus the bead chain and other parts are mounted again easily.