Abstract: To get the appropriate composition of proportion for the polyculture of H.discus and seaweed, this study can be divided into two parts.First, different density of seaweeds (U.lactucaand G asiatica) were set to grow in effluent from aquaculture for 24 hour, of which the content changing of NH+4-N, NO-2-N, NO-3-N, PO3-4-P were tested.The result showed that the purification effect was upregulated with the increase of the density.Because too much seaweed would hinder the abalone's growth, we chose the suitable density of 3g·L-1 and 6g·L-1 for U.lactucaand G asiatica.Second, we set different density of H.discus for polyculture with 3g·L-1 of U.lactucaand 6g·L-1 of G asiatica, respectively, and discovered that with the increase of H.discus density, its growth speed went down respectivly.The growth speed of H.discus of the 400 per pond group showed no significant difference with that of the 200 per pond group, but significantly different with which of the 600 per pond group, thus we regarded the density of 400 per pond as the appropriate one for H.discus.And the result also showed that when the density of H.discus was constant, U.lactucacould provide better purification effect then G asiatica, and higher growth speed of H.discus as well.