This research investigates the influence of the reacting force which suffered from the handle of a hammer to strike an object. To achieve the study purpose, an impulse on the hammer face in a very short time was investigated. The researcher used computer-aided design software Solidworks to set up the hammer model and he used finite element software LS-DYNA to analysis the dynamic problem of the hammer by impulse loading. This study aims to find out the reaction force at the gripping position of different shape of cross-section, length, gripping position and angle of the handle and compares the results along x, y, and z axis respectively. After summing up an optimum handle shape and gripping position, users can operate the tool easily. The optimum also reduces the probability of musculoskeletal disorders. It is expected the study findings can not only provide some reliable data for the reference in hammer manufactures but also make a breakthrough in computing aided engineering.