Hemocyanin, a copper containing protein, is the respiratory protein of Crustacea. Here, 4 major hemocyanin molecules in the hemolymph of Scylla olivacea were purified and studied. Both two-hexamer (24S) and hexamer (16S) form of hemocyanin are present in all adult¡¦s hemolymph. In vitro, 24S hemocyanin dissociates into two 16S hemocyanin in the absence of calcium under high pH value (> 8.9). Little of 16S hemocyanin assembles spontaneously into 24S hemocyanin after calcium is added. Both 16S and 24S hemocyanins were purified from hemolymph, the 16S hemocyanin differs from the 24S hemocyanin in the presence of intersubunit disulfide bonds, it is inferred that not all native 16S hemocyanin dissociates from 24S hemocyanin. Besides the 24S and 16S hemocyanin, there are two massive proteins in the hemolymph of ovary-maturing female S. olivacea. One is female-specific hemocyanin (FSH), which occurs in the hemolymph of ovary-maturing females, but not in the hemolymph of juveniles of either sex or in adult males. FSH is confirmed as a hemocyanin due to its copper content and oxygen binding ability. FSH is also found in ovary, embryo and early-stage zoea, and is proposed to be an important hemocyanin that supplies enough oxygen for ovary-maturing female crab, egg, embryo and early-stage zoea. Another massive hemolymph protein is a non-respiratory protein (NRP) that is present in hemolymph of adults of both sex, the molecular mass of its subunits is similar to hemocyanin and FSH, and one of subunits can be slightly recognized by anti-FSH antibody. NRP is not a respiratory protein, there is neither copper containing nor absorbance of 340nm. FSH and NRP, especially NRP, contain more carbohydrates than the 16S hemocyanin.