Taking the 4th-instar larval Propsilocerus akamusi as test object, this paper studied the acute toxicity of phenol, and the body mass, pupation rate, protective enzyme activities, and detoxifying enzyme activities of the larvae under exposure to phenol. The LC50 value of phenol to the larvae after exposure for 6, 24, 48, 72, and 96 h was 222.52, 134.86, 67.74, 47.39, and 35.76 mg x L(-1), respectively, and the dry mass, fresh mass, and pupation rate of the larvae decreased under the exposure of 0. 4, 4, and 40 mg phenol x L(-1). During 72 h exposure to phenol, the larval catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), and carboxylesterase (CarE) activities responded to phenol in concentration- and time-dependent way, while the acid phosphatase (ACP) and alkaline phosphatase (ALP) activities responded slowly and were only inhibited significantly under the exposure to 40 mg x L(-1) of phenol for 48 and 72 h, respectively. It was suggested that the body mass, pupation rate, and CAT, SOD, GST, and CarE activities of 4th-instar larval P. akamusi could be used as the biological markers to monitor the phenol pollution of water body.