The application of InGaAs focal plane arrays (FPAs) desires high density and small pixel pitch, and the smaller the pixel pitch, the stronger the pixel coupling. By fabricating 5 μm pitch InGaAs arrays with different scales, the pixel coupling effects in high-density InGaAs arrays were studied. Innovatively, matrix equations were introduced to describe the contributions of dark current from each part, constructing a mathematical model of pixel coupling and the contributions of dark current resulting from coupling effects were quantitatively analyzed. The results indicated that at a bias voltage of -0.1 V, the reverse-biased pixels in the array can suppress the dark current of adjacent reverse-biased pixels by 21.39% of the pixel's initial dark current. In contrast, zero-biased pixels can increase the dark current of adjacent reverse-biased pixels by 219.42%. Based on the high-density focal plane pixel coupling model, the impact rules of pixel coupling on dark current have been summarized, providing new insights for the dark current research in high-density InGaAs focal plane arrays.