Objective To explore the effects of Shihusan on the intracellular free calcium of human retina cells and the protection from the damage of glutamate. To investigate its function and mechanism in retinal degeneration diseases, and to offer the basis on which to treat the similar disease clinically. Design Experimental study. Participants Retinal cells from normal human eye. Methods Cultivation of human retinal neural cells was perfonned. The changes of fluorescent density of intracellular free calcium of cultured cells labeled with Fluo3/AM before and after adding Shihusan and verapamil were detected with laser scanning confocal microscopy. In addition, the effect of Shihusan on calcium overload provoked by glutamic acid was observed. Main Outcome Measures The level of intracellular free calcium of retinal cells. Results The retinal cells adhered, spread and grew well in vitro. The fluorescence intensity increased 88% in glutamic acid group, decreased 14.8% and 57.3% in Shihusan group and verapamil group respectively. Shihusan couldn't decrease the intracellular Ca2+ that was increased by glutamic acid, but could inhibit the increasing tendency induced by glutamic acid. The difference was significant compared to control group (P=0.000). Conclusions Shihusan might decrease the level of intracellular free calcium in cultured human retinal cells, and resist the damage of glutamate. Its mechanism was related possibly to resisting calcium overload and inhibiting apoptosis.