Abstract Leakage flow loss is an important factor affecting the aerodynamic efficiency of turbines. In this paper, experimental and numerical computational studies were used to investigate three different tips of a highly loaded turbine rotor. The single-cavity tip formed by squealers was considered as the original structure. Based on this, two improved structures were developed, namely, cavity winglet tip (CWT) and double-cavity combined winglet tip (DCWT). Five-hole probe and oil flow visualization were used for experimental studies, and numerical calculations were used to analyze vortex system structure and loss development. It was found that the double-cavity combined winglet tip structure can effectively change the vortex structure inside the cavity and reduce the leakage flowrate. At the same time, the aerodynamic performance was optimized by 4%.