The precision of tracking and targeting, the divergence angle of the laser beam emitted by the laser ranging sensor, the detection field of the laser echo receiving system, particularly for small targets also related to the range and detection probability of laser ranging are all factors that influence the requirement of parallelism of the optical axis of the optoelectronic tracker. This paper examines the properties of energy distribution of illuminated beam, takes into account temperature, vibration, and other environmental factors, as well as the optical axis stability error caused by variable focusing, and proposes the calculation method of optical axis parallelism requirements of optoelectric tracker based on the principle and index requirements of laser ranging of optoelectronic tracker. Moreover, the optical axis parallelism error distribution model is established, and the general control requirements and estimation methods of each random error term and each calibration residual error term are discussed. This information serves as a guide for the design and analysis, manufacturing process, and maintainability improvement of the optoelectric sensors while taking into account their maintainability for in-place replacement and field calibration.