<p>Titanium alloys are widely used in practical applications, but the thin sheet is difficult to machine due to the cutting force and heat affected zone (HAZ) which could cause seriously warping deformation. Aiming at solving this problem, a new compound processing method of gas-waterjet assisted laser cutting (GWLC) was proposed. The processing mechanism and characteristics of Ti-6Al-4V thin sheets were experimentally studied, and a comparison was made with the gas jet assisted laser cutting (GLC). The effects of jet parameters on kerf width, taper angle, and surface roughness of the cross-section were discussed, and the optimum process parameters to achieve high-quality cutting were obtained. Experimental results show that a clean kerf with a smooth cut surface can be achieved at high material removal rates. Moreover, the upper kerf width can be increased by 108.9%; the HAZ is reduced by 32%; and the taper angle is decreased by 33%. GWLC promotes the oxidation reaction, and the grains generated are finer than those in GLC. Better processing performance is shown when the gas pressure is increased to 0.3 MPa or higher, which indicates that the coaxial gas jet can reduce the interference of the water flow and enhance the laser ablation effect. When the waterjet impact angle is increased to 60°, a smoother cutting surface can be obtained under high waterjet pressure.</p>