Objective To investigate the influence of different hardness bolus on bite force and the functional characteristics of masseter and temporalis-anterior muscle during unilateral maxmal biting. Methods PVC film was placed on the surface of mandibular second premolar and the first molar on one side of the subject, the contralateral same teeth were placed in doughy acrylic. Then the acrylic resin piece was made by maxmal biting.Using T - Scan Ⅲ bite analyzer and Bio-Pak EMG the bilateral maximum bite force and masseter and temporalis-anterior muscle activity were measured under ICP and unilateral biting. Results (1)During ICP maxmal biting,no differences was found in EMG activity between bilateral temporalis-anterior muscles or between bilateral masseters.(2) During unilateral maxmal bitting , bilateral side of masseter muscle activity had no obvious difference (P>0.05), but EMG activity of the temporalis-anterior muscle on the biting-side(147.75±31.37)μν,(145.70±35.08)μν were higher than that of the contralateral side(115.87±24.08)μν,(121.24±22.78)μν (P<0.05).(3)During unilateral maxmal biting, masseter muscle activity had no obvious statistically significance when compared with ICP maximal biting(P>0.05), but the contralateral temporalis-anterior muscle values(147.75±31.37)μν and (145.70±35.08)μν were much smaller than that of ICP maxmal biting(136.88±29.54)μν, the difference was statistically significant (P<0.05). (4)Unlateral occlusion, all the subjects (20/20) had the contralateral occlusal contact phenomenon. The bite force of soft bolus (9174.60±955.29)raw was bigger than that of he hard bolus(6156.70±979.27)raw (P<0.05). But the masseter and temporalis-anterior muscle activity in soft bolus had no obvious difference when compared with hard bolus (P>0.05). Conclusions Compared with hard bolus, the bite force of soft bolus is relatively smaller than that of hard bolus, the influence of different hardness of occlusal bolus has no significant effect on masticatory muscle.