ing at the bottleneck of telephoto camera calibration, a novel calibration method based on conics and line fusion features is proposed. The article reveals the formation mechanism of ill-conditioned calibration equation of the telephoto camera. Given that the cross ratio and tangent point are basic projective invariants, a concentric semi-circular template is designed. Combined with the normalized line homography estimation method and the partitioned regularization estimation algorithm, the high-precision solution of initial values of intrinsic and extrinsic parameters of the telephoto camera is obtained. Further, considering the lens distortion, the integral distance between line segments is introduced, taking the minimum distance from the model line to the projection plane as the cost function, and a nonlinear optimization algorithm is adopted to refine the calibration parameters. Simulation and actual experimental results show that the proposed calibration method of the telephoto camera is effective, and has higher accuracy and robustness compared with the traditional method.