The acute toxicity and the joint toxicity of Zn2+ and Cr6+ on Hydra (LC50 ) were stud-ied and the change of soluble protein of Hydra after stressed by Zn2+ andCr6+ wasdeterminedby the static test method .The results showed that the toxicity sequence of two heavy metals ions to Hydra was Cr6+ > Zn2+ .The LC50 of 24 ,48 ,72 and 96 h for Zn2+ to Hydra were 1.037 5 , 0.947 6 ,0.628 6 and 0.533 3 mg/L ,while for Cr6+ ,the LC50 were 0.594 7 ,0.475 0 ,0.264 7 and 0.121 4 mg/L ,respectively .The safe concentrations of Zn2+ and Cr6+ were 0 .053 3 mg/L and 0.012 1 mg/L ,respectively .The toxicity of combined Zn2+ and Cr6+ was greater than the individ-ual toxicity ,representing a result of the synergetic effect .The soluble protein content of Hydra was increased first and then decreased accompanying with the raised Zn2+ and Cr6+ concentration .%为探讨Z n2＋、C r6＋对水螅的急性毒性作用及其联合毒性作用，采用静水法生物测试，测定了经Z n2＋和C r6＋胁迫后水螅体内可溶性蛋白含量的变化。结果表明，C r6＋毒性大于Z n2＋。Z n2＋和Cr6＋对水螅24、48、72、96 h的半数致死质量浓度（LC50）分别是1.0375、0.9476、0.6286、0.5333 m g/L和0.5947、0.4750、0.2647、0.1214 m g/L ；二者的安全质量浓度分别为0.0533 m g/L、0.0121 mg/L。Zn2＋、Cr6＋对水螅的联合毒性大于单一毒性，表现为协同作用。随着重金属离子浓度的增高，水螅体内的可溶性蛋白质的含量表现为先上升后下降。
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