The performance of a hydrogen-blended gasoline engine at lean and the wide open throttle conditions was investigated. A hydrogen port-injection system was adopted to introduce the hydrogen into each cylinder. The engine was operated at 1400 rpm and two hydrogen blending levels of 0% and 3%. The excess air ratio was raised from 1.00 to about 1.45 for a given hydrogen addition fraction. The test results demonstrated that the hydrogen blending contributed to the raised thermal efficiency and shortened flame development and propagation durations. An increased brake mean effective pressure was found after the hydrogen addition only at lean conditions. For both stoichiometric and lean conditions, the hydrogen blending was beneficial for reducing the engine cyclic variation. This provides a possibility to run a hydrogen-blended gasoline engine with the fully opened throttle position and control the engine torque only by adjusting the excess air ratio. Toxic emissions including HC, CO and particulate were reduced after the hydrogen blending. (C) 2014 Elsevier Ltd. All rights reserved.