The invention discloses a breeding method for shortening float periods of urechis unicinctus larvae. The breeding method particularly includes feeding isochrysis 3011 to the urechis unicinctus larvae from the third day to the seventh day after the urechis unicinctus larvae are fertilized, and keeping the temperatures at 15.5-16 DEG C; keeping the water temperatures at 16.5-17 DEG C from the seventh day to the twelfth day; keeping the water temperatures at 17.5-18 DEG C from the thirteenth day to nineteenth day and changing 1/2 volumes of water twice on a daily basis; feeding feed four times on a daily basis from the seventh day to nineteenth day. The isochrysis 3011 is initial feed, and the feeding quantities of the initial feed is 40ml/m<3>d. Formulas and usage quantities of the feed in different procedures from the seventh day to nineteenth day are different from one another. The breeding method has the advantages that the metamorphosis and settlement time of the urechis unicinctus larvae in the float periods can be shortened, breeding periods can be shortened by 15-25 days as compared with schemes in the prior art, and the breeding cost can be reduced to a great extent.