The object of this study is to understand the effect of food on the speed of ciliary movement of the gill of cultured hard clam. It is known that the speed of ciliary movement of the gill of cultured hard clam is affected by temperature and salinity, so this study explores the influence of food on speed of ciliary movement of the gill under the different temperature-salinity conditions. This study used three methods to test for the speed of ciliary movement of the gill of cultured hard clam. By the first method, using a piece of aluminum foil tested for the gill in vivo, demonstrated none of Isochysis galbana¡BSynechococcus sp.¡Btemperature¡Bphase and sizes of aluminum foil affected significantly on the speed of ciliary movement of the gill of cultured hard clam. By the second method, using sand tested for the gill in vitro, demonstrated adding I. galbana or the high concentration (1¡Ñ105 cells ml-1) of Tetraselmis chui caused the speed of ciliary movement of the gill of cultured hard clam increased significantly at room temperature, 15 psu. At 32¢J, only the low concentration(1¡Ñ103 cells ml-1) of I. galbana affected significantly the speed of ciliary movement of the gill, and the mean speed of 1.36 cm/min at 32¢J was slower than the mean speed of 2.05 cm/min at room temperature. At 10 psu, both high and low concentration of I. galbana influenced the speed of ciliary movement of the gill, besides the mean speed of 2.82 cm/min at 10 psu was faster than the mean speed at 25 psu. The ciliary movement of the gill of cultured hard clam had no response to I. galbana, and the mean speed of 1.76 cm/min at 25 psu. By the third method, using sands tested for the gill in vivo, the results showed that adding the high concentration of I. galbana caused the speed of ciliary movement of the gill of cultured hard clam to increase significantly, and 33.85¢H of the change of this speed was not different significantly with 33.00¢H of the change of the speed of the gill in vitro adding the high of I. galbana. Besides, the mean speed of 1.99 cm/min by using sands tested for the gill in vivo was not also different significantly with the mean speed of the gill in vitro.Based on the above results, the result tested the gill in vitro by the second method was similar to the result tested the gill in vivo by the third method. Under the same condition, the maximum change of speed of ciliary movement of the gill was about sixty percent from the experiment of adding the low concentration of I. galbana, and the minimum change of speed was about ten percent from the experiment of the low concentration of T. chui. The change of the speed of ciliary movement of the gill of cultured hard clam was most affected by I. galbana, and the change was about thirty percent.