Abstract: Laser welding-brazing tests of 6061 aluminum alloy and Q235 steel were carried out by AlSi12 flux-cored welding wire without Cs and with Cs as filler metal. Macrostructure and microstructure of welded-brazed joints were analyzed by optical microscope and scanning electron microscope. Influence of Cs element on wetting and spreading ability of flux-cored welding wire on the steel surface, microstructure and tensile properties of welded-brazed joints was discussed. The research results showed that adding Cs element into flux-cored welding wire improved wetting and spreading ability of molten welding wire on the back of base metal, resulting in a full and beautiful appearance of Al alloy/steel laser welded-brazed joints. Cs elements transferred into Al alloy/steel welded-brazed joints through metallurgical reaction, and it hindered reaction between Al and Fe, so that thickness of intermetallic compound layer (IMCs) was decreased at the interface of welded-brazed joints. Moreover, tensile strength of welded-brazed joints was reduced.