Abstract: The 5×5 square GRIN lens array was manufactured with the ion-exchanging technique and precision processing technology. The imaging properties of the array were studied. The results show that, compared with circular aperture GRIN lens array, the square aperture GRIN lens array can effectively increase the filling coefficient and active optical area, and its multiple image and synthetic image have better imaging quality. The reasons of the multiple image′s deflection and synthetic image′s deformation are analyzed. The solution for the problem is presented.