To investigate the relationship of surface electromyogram (sEMG) and handgrip force, a measurement system was developed. Ten healthy subjects were required to perform a series of static contraction trials by maintaining the force level with maximal voluntary contraction (MVC), 75%MVC, 50%MVC and 25%MVC respectively. Then they sustained MVC as long as possible until fatigue. The handgrip force and sEMG on the forearm muscles were recorded. Root mean square (RMS), mean power frequency (MPF) and median frequency (MF) of the sEMG were calculated with LabVIEW. The results show that RMS increased with force level during voluntary contraction, while MPF and MF shift to lower frequency during fatigue condition. These findings suggested that the designed system can be used to study forearm function.