Aiming　at　a　mass　variation　of　unmanned　surface　vehicle　and　the　poor　or　even　unmeasurable　signal　of　yaw　rate　signal,　the　dynamic　output　feedback　H∞　control　method　is　proposed　for　heading　regulation　based　on　improved　bounded　real　lemma　to　reduce　the　conservativeness　and　guarantee　the　robustness.　First,　a　linear-varying-parameter　heading　error　model　with　external　disturbances　is　established　by　the　consideration　of　mass　as　a　variable　parameter.　Second,　the　dynamic　output　feedback　controller　with　H∞　performance　is　presented　for　the　linear-varying-parameter　heading　error　model,　and　its　nonlinear　matrix　inequality　conditions　for　the　stability　of　the　closed-loop　system　are　deduced　from　improved　bounded　real　lemma　by　parameter-dependent　Lyapunov　to　maintain　the　system　robustness.　Furthermore,　the　solution　of　nonlinear　matrix　inequality　conditions　relies　on　the　variable　substitution　method,　and　improved　bounded　real　lemma　reduces　the　conservativeness　of　the　controller　design　by　introducing　auxiliary　relaxation　variables　to　derive　the　equivalent　linear　matrix　inequality　condition.　Finally,　the　heading　control　simulations　for　unmanned　surface　vehicle　indicate　that　the　dynamic　output　feedback　H∞　method　based　on　improved　bounded　real　lemma　(IDOF)　is　robust　to　system　parameter　variations　and　external　disturbances,　and　can　effectively　reduce　the　conservativeness　of　the　controller　design.　Moreover,　dynamic　output　feedback　H∞　method　based　on　improved　bounded　real　lemma　has　faster　transient　processes　and　smaller　steady-state　errors.　©　IMechE　2023.