The invention relates to a curtain security structure driven by a bead chain, comprising an upper assembler, a lower assembler, and flexible support parts to be assembled correspondingly. A lower rotary wheel of the lower assembler is engaged with an upper rotary wheel of the upper assembler. The two flexible support parts are inserted from the bottom of the lower assembler to assemble the upper and the lower assemblers. An upper bead chain and a lower bead chain are entwined and disposed in upper and lower bead pockets respectively via pockets disposed on struts of the flexible support parts. When children improperly use the curtain security structure and thus are entwined by the lower bead chain and struggle, the lower bead chain, the lower assembler and the flexible support part can simultaneously detach from the upper assembler to prevent the children from being damaged to achieve the safe protection effect.