Abstract: Silver nanoparticles (TMA-AgNPs) functionalized by thiomalic acid were prepared. The interaction between the functional groups of the TMA-AgNPs and Al³⁺ resulted in the aggregation of TMA-AgNPs accompanied by a color change from yellow to orange with increase of Al³⁺ ion concentration. Based on this fact, spectrophotometry was applied to the determination of aluminum in flour foods. The optimized conditions found were as follows:① amount of 5.0 mmol·L^-1 thiomalic acid solution was 2 mL; ② modification reaction time was 10 min; ③ interaction time of Al³⁺ and TMA-AgNPs was 2 min. Linearity range of Al³⁺ was found between 0.10 μmol·L^-1 and 5.00 μmol·L^-1 with detection limit (3S/N) of 0.031 μmol·L^-1. The proposed method was applied to the analysis of samples of flour foods, giving values of recovery found by standard addition method and RSDs (n=5) of determined values in the ranges of 97.0%-105% and 2.1%-3.1% respectively.