Abstract: For the study of test method of alkylphenol polyethoxylates in solution, the Nonylphenol ethoxylates (NPEO) and Octylphenol ethoxylates (OPEO) were used for the investigation of their UV spectroscopy. The spectroscopy show that the spectroscopic curve of two chemicals has no significant differences, and has characteristics absorption at 275nm and 224nm, which could be used for qualitative and quantitative analysis of APnEO in the solution. For the absorbance at 224 nm, it has higher sensitivity but narrow linear range of APnEo concentration, while for the absorbance at 275nm; it has relatively low sensitivity but wide linear range of APnEo concentration. The molecular weight of APnEO will affect the linear range of the concentration.