The invention discloses an organ fibrosis-preventing oral solution prepared from an Eucheuma muricatum extract. The oral solution comprises the following components: in percent by mass, 0.5-2% of mucilage, 0.2-1% of a preservative, 0.1-1% of a co-solvent and the balance Eucheuma muricatum extract. The preparation method of the Eucheuma muricatum extract includes the following steps: (1) washing Eucheuma muricatum; (2) taking the step-(1) washed Eucheuma muricatum with a quality of M1, adding water of a quality M2, then performing homogenizing, sterilizing, filtration and centrifugation sequentially, collecting the supernatant, and then performing ultrafiltration by using an ultrafiltration membrane system with 0.1 micron microporous membranes, molecular weight cut-off of 5,000 Daltons andoperating pressure difference of 0.1-0.5 MPa so as to obtain the Eucheuma muricatum extract Extract, wherein the ratio of M1 to M2 is 1:(8-12). The prepared oral solution has remarkable efficacy in treatment of organ fibrosis, and has a better effect on treatment of organ fibrosis than pirfenidone and Nintedanib, and in addition, compression ultrafiltration of the ultrafiltration membrane system is adopted by the preparation method of the Eucheuma muricatum extract, and the efficiency is better than that of a chromatography extraction technology.