[Objectives]  Pest control indices are the main basis for optimizing decision-making in pest management systems. This study focused on the relationship between the amounts of damage caused by Lygus pratensis（Linnaeus）and cotton yield loss in different growth periods in Xinjiang. This control index was studied to improve L. pratensis control methods. [Methods]  Using the square regression, and orthogonal rotation, designs, the regression equation for the relationship between the L. pratensis abundance and cotton yield loss rate at the budding, flowering, and bolling stages, were determined. In combination with the economic loss to cotton producers, the control indices of L. pratensis during the budding, flowering, and bolling, stages were calculated. [Results]  The regression equation is: Y=12.906+5.273X₁+4.780X₂+2.365X₃+4.588X₁²+3.331X₂²+ 2.910X₃². The greatest reduction in cotton yield occurred at the budding stage, followed by the flowering stage with the least loss occuring during the bolling stage. The control indices of L. pratensis during the budding, flowering, and bolling, stages were 12 adults per 100 plants, 20 adults per 100 plants, and 41 adults per 100 plants, respectively. [Conclusion]  Control indices for L. pratensis can be calculated for different stages of cotton growth. This approach is practical, readily mastered by cotton farmers, and could provide a theoretical basis for the prevention and control of L. pratensi in Xinjiang.