The concentration detection method and results of a viscosity reducer play important roles on its structure design and usage method. To realize the concentration analysis of a novel viscosity reducer used in shengli oilfield， a high-performance liquid chromatography method with a hydrophobic column was established for water and oil phase samples，and the distribution regulations of concentration in different phases were investigated. The results showed the lowest limit of detection for water phase sample was 10 mg/L， the broad linear range was 10—3000 mg/L and relative standard deviation was less than 5%. Combined with gradient solvent extraction technique， the viscosity reducer existing in the oil phase could be efficiently extracted and separated from oil samples， and then could be analyzed adopting above established analytical method. The extraction efficiency was over 95%. As for crude oil/viscosity reducer binary system（the mass ratio of kerosene and crude oil was 1∶2， and the mass ratio of oil sample and 3% mass fraction of viscosity reducer solution was 1∶1）， over 80% viscosity reducer distributed in water phase， and the content in oil phase slighted increased with the increase of temperature. As for crude oil/viscosity reducer ternary system（the mass ratio of kerosene and crude oil was 1∶1， and the mass ratio of oil sample and 3% mass fraction of viscosity reducer solution was 1∶1）， there was nearly no viscosity reducer in oil phase， about 75% of viscosity reducer distributed in emulsion phase and the minority was in water phase. With the increase of temperature， the content in water phase increased. Under the condition of salt solution， the content in water phase was little more than that with pure water solution， however， the content was almost similar to each other under the conditions of various concentration salt solution.