The aim of research is to find out the effect of tethered swimming for freestyle speed. Thirty-five people have been tested and randomly divided into Control Group and Experiment Group. Before the test, the Experiment Group has been trained with tethered swimming for 8 weeks, and then put the results of the tow groups through T test statistically analysis and sum up the below conclusion: (一) Tethered swimming is obviously effective for the speed on men's 25-meter freestyle (t=4.l4*) and 50-meter freestyle (t=4.06*). (二) Tethered swimming is obviously effective for the speed on women's 25-meter freestyle (t=3.23*) and 50-meter freestyle (t=2.25*). Generally speaking, tethered swimming is obviously effective for the speed on freestyle.