Abstract: Objective The honeycomb structure of high temperature titanium alloy Ti65 is very important for the development of new aircraft. It is of great value to study the influence of brazing process parameters on its interface structure and mechanical properties. Methods In this study, the brazing process test was carried out on the plate/plate structure, and the interface structure and mechanical properties were analyzed. Subsequently, the honeycomb sandwich structure was brazed, and its interface structure and mechanical properties were analyzed accordingly. Results When the brazing temperature is low or the holding time is short, there are more bulk and needle-like Ti-Cu and Ti-Ni intermetallic compounds at the interface. Increasing the brazing temperature or prolonging the holding time, the bulk intermetallic compounds at the interface gradually decrease or even disappear. When the brazing temperature is 950 ℃ and the holding time is 30 min, the interface structure and mechanical properties are the best. The interface structure is mainly composed of acicular α structure. Ti-Cu and Ti-Ni intermetallic compounds are dispersed between the acicular α structure. After removing the surface oxygen-rich layer, the tensile strength, yield strength and elongation of the plate/plate brazed composite plate are 1118.77 MPa, 1036.61 MPa and 5.95%, respectively. Under this process parameter, the plate/core brazing interface in the honeycomb structure is mainly composed of needle-like α structure. The three-point bending strength, flat compressive strength and edgewise compressive strength of the sandwich structure at room temperature are 207.66 MPa, 20.60 MPa and 1 352.70 MPa, respectively. As the test temperature increases, the mechanical properties of the honeycomb sandwich structure gradually decrease. At 650 ℃, the three-point bending strength, flat compressive strength and edgewise compressive strength are 39.97%, 43.16% and 30.97% of the room temperature strength, respectively. Conclusion Under the process parameters of 950 ℃ and 30 min, the Ti65 plate/plate and honeycomb sandwich structure are dominated by needle-like α structure and the high-quality interface structure with dispersed intermetallic compounds, which has excellent room temperature mechanical properties, but its high temperature strength decreases significantly with the increase of temperature.