The existing internal calibration methods of a linear array CCD camera generally depend on the distortion parametric model, and the calibration accuracy is limited by the correlation of internal parameters of the model. Herein, an internal calibration method of linear array CCD camera using a nonparametric model is proposed to improve the internal calibration accuracy. Through the pinhole imaging model and the perpendicular method, a nonparametric model of linear array CCD camera imaging is constructed, and the mapping relationship between spatial feature points and imaging points and the size of the distortion between the ideal imaging point and the actual imaging point are directly determined. The reprojection error is used as the evaluation standard to compare the proposed method with the internal calibration method using the parametric model. The experimental results show that the root mean square, average value, and maximum value of the reprojection errors obtained using the proposed method are 0.42, 0.00, and 0.95 pixel, respectively, which are 0.80, -0.10, and 2.47 pixel less than that obtained using the internal calibration method using the parametric model.