We propose a multiwaveguide cavity which can significantly enlarge the mode volume of distributed feedback (DFB) cavity without increasing the cavity length. The cavity is constructed by combining shifted DFB cavity with contra-directional couplers. Different from single-waveguide DFB cavity, the resonant mode is oscillating in multiple waveguides. A smaller threshold gain density is also obtained compared to single-waveguide DFB cavity. Theory model of the multiwaveguide cavity is established and finite-difference time-domain simulation is performed to verify the model.