In order to achieve beam combination of volume Bragg grating diode lasers (VBLs) in the external cavity, characteristics of VBL with long cavity length is studied. A plane convex cylindrical lens with focal length of 25 mm is used to collimate the single emitter laser diode (LD) in slow axis direction. Meanwhile, volume Bragg grating (VBG) is positioned off-axis in fast axis of the LD. External cavity length of about 240 mm is established, and the linewidth is narrowed from 1.8 nm of free-running diode to 0.14 nm. In the experiment, characteristics of the VBL are unchanged for different polarizations of laser. By adjusting the VBG′s temperature, a tunable range from 779.18 nm to 779.75 nm of the VBL with long cavity length is realized while the linewidth remains the same.