Morin was employed as complexing reagent in determining inorganic monomeric Al in acidic soil solution using a reversed-phase high-performance liquid chromatograph and a fluorescence spectrophotometer in this study.Three different methods,varying only in molar ratio of morin:Al,dissolving medium of the complexing reagent,and pH of the buffer solution,were proposed for comparison in linear range,accuracy,and precision,and analyzed for correlation between them.Results showed that Method Ⅲ (1.0×10^-4 mol L^-1 Morin dissolved in ethanol reacted with inorganic monomeric Al in pH 410 acetate buffer solutions,and fluorescence was recorded by fluorescence spectrophotometer (Ex=403.3nm,Em=490nm) ) was the most suitable one for determing inorganic monomeric Al in acidic soil solution.