The invention discloses a ladder rope structure for venetian blinds, and aims to provide a ladder rope for venetian blinds, which allows for less deformation, allows for easy opening and closing of blades and has long service life. The ladder rope structure comprises a pair of longitudinal cords and a pair of transverse cords; each longitudinal cord includes a core cord and tensile cords, the twosides of the core cord are respectively provided with a left hooking cord and a right hooking cord which are in hooked joint, the tensile cords are respectively connected with the left hooking cord and the right hooking cord and are tightly attached to the front surface and back surface of the core cord, and the left hooking cord, the right hooking cord and the tensile cords wrap the core cord; the pair of transverse cords are respectively and alternately connected with the pair of longitudinal cords to form a plurality of transverse gaps. The ladder rope structure has the advantages that thescattered ladder rope extends longitudinally, so that the defect is overcome that the blades of a venetian blind are not opened or closed properly due to the fact that the longitudinal cords are extended longitudinally. Flexible opening and closing of the blades of the venetian blind is ensured, and the service life of the venetian blind is prolonged. The ladder rope structure is reasonable in structure, convenient to manufacture, and convenient to popularize.