To investigate the binding property between β-lactoglobulin (β-LG) and monascus pigments (Mps) under different pH values (2.6,6.2,7.1,8.2), four kinds of complex systems of β-LG and Mps were prepared, and the interactions between them were characterized using fluorescence spectroscopy, circular dichroism (CD) spectrum and molecular docking methods. At the same time, the antioxidant activity, thermal stability, and photo-stability of the complex (β-LG&Mps) were also determined. The results showed that the binding of Mps to β-LG could induce fluorescence quenching of β-LG under the experimental pH range. The complex of β-LG and Mps was mainly maintained through Van der Waals force, hydrophobic interaction and hydrogen bonds. However, no significant changes were observed in the secondary structures of β-LG. The DPPH free radical scavenging capacity of β-LG&Mps complex was higher than that of either β-LG or Mps, but lower than the sum of the two components, indicating that β- LG and Mps exhibited antagonistic effects on DPPH free radical scavenging. After forming complex with β-LG, compared with uncomplexed Mps, the retention rates of Mps in the complex increased by 58% (pH 6.2), 30% (pH 7.1) and 24% (pH 8.2), respectively, at 50℃. Additionally, the retention rates of Mps in the complex increased by 65% (pH 6.2), 43% (pH 7.1) and 43% (pH 8.2), respectively, under a light intensity of 600 Lux for 36 h at temperature 25℃. β-LG improved the thermal and photo-stability of Mps at pH values 6.2,7.1, and 8.2, however, the thermal stability and photo-stability of Mps were poor under the acidic condition (pH 2.6). The study explored the improvement of the stability of monascus pigment through the interaction of food components, to provide beneficial references for the development of monascus pigment related products.