Abstract: Two designed Ni-based filler alloys were used to join DD6 single crystal superalloy to investigate the function mechanism of tungsten in the TLP diffusion bonding process of single crystal superalloy. The effects of tungsten on the joint microstructure and mechanical properties were investigated. The isothermally solidified process of brazing alloy containing tungsten conducts slowly. After brazing for 30 min, the joint of brazing alloy without tungsten exhibits higher elevated temperature strength. With the extending of holding time, the elevated temperature strength of both joint increase obviously, where the increase value of joint for brazing alloy with tungsten is higher. It indicates the strengthening effect of tungsten on the joint after isothermal solidification. The elevated temperature strength of DD6 single crystal joint at 1000 ℃ reached 639 MPa after brazing for 120 min with Ni-Cr-Co-Ta-Al-W-B brazing alloy, which is 90 percent of DD6 base material.