In order to improve the spot position detection accuracy for 1 550 nm near infrared band, an innovative infinite integral model was proposed. At first, the relationship between InGaAs four-quadrant detector(QD) output signal and the spot real position was deeply analyzed where the laser spot energy displayed a Gaussian profile. By taking into account the error effects of detector diameter and gap size, and introducing the position error compensation factor, an effective spot radius was obtained with a best fit using the least square method, and then a new analytical expression was proposed. Finally, the experiment was made for verifying the performance of our new model in the established InGaAs QD spot detection system. The results of simulation and experiment show that the new model could effectively reduce the spot position detection error for different radii; when the total energy of incident light is about 10 μW, the beam radius is 0.75 mm, in the detection range of [-0.75-0.75 mm], the root-mean-square error of 0.003 mm and the maximum position error of 0.009 mm with the new model, are reduced 78.6% and 52.6% than the original model, respectively. Therefore, the new model would have a good prospect in the engineering practice of laser communication or laser radar.