Objective To analyze forearm-rotational effects on muscle electric activities of upper-limb during push-up. Methods The EMG of long and lateral heads of biceps brachii, anterior and medius deltoid, pectoralis major and biceps brachii for ten subjects during push-ups at three forearm rotations of internally rotated 90° (IR90), hand-neutral (NEU), and externally 90° (ER90) was collected. The root mean square (RMS) values of EMG were calculated and normalized. To determine whether there were differences between the EMG from the three positions, a One-Way ANOVA with factor rotational position was conducted on the normalized RMS values. The EMG profiles through a cycle were also displayed. Result From IR90 to ER90, there was no significant difference for the long head of biceps brachii, but a decrease for the lateral head of biceps brachii and medius deltoid, and an increase for anterior deltoid, pectoralis major and biceps brachii. The EMG profiles showed three patterns. Conclusion There were differences of electric activities for the muscles studied during push-ups at various forearm positions. However, these changes did not occur in the same way for the six muscles.