The removal effects and the first order reaction kinetics of 2, 4-DCP with PS and UV/PS were compared, respectively. The effect of oxidant (PS) dosage, different initial 2, 4-DCP concentration and humic acid on the photolysis reaction were investigated. The vibrio-qinghaiensis sp.-Q67 was applied to evaluate the environmental toxicity of 2, 4-DCP solution and successive transformation products during UV/PS process. The results showed that the removal percentage of 2, 4-DCP was only 4% for the only PS process, while the degradation percentage reached higher 96.4% with UV/PS process, which showed the 2, 4-DCP was effectively degraded by UV/PS process compared with the PS alone. Meanwhile the pseudo-first-order reaction equation could well describe the 2, 4-DCP degradation behavior and the k_obs (reaction rate constant) was 35.1×10^-3min^-1 in UV/PS process. The degradation efficiency and rate constant rate increased with the increasing of the oxidant (PS) dosage, decreased with the increase of initial 2, 4-DCP concentration. The coexisting HA promoted the 2, 4-DCP degradation at the beginning and then gradually inhibited the degradation. For toxicity evaluation experiment, Luminescent bacteria inhibition rate decreased with the decrease of concentration of 2, 4-DCP and the increase of intermediate products, which indicated the reduction of environmental toxicity of the reaction system. According to the multiple experimental results, the relative inhibition rate of luminescent bacteria had no relation with exposure time of luminescent bacteria under the same oxidation time.