With the continuous development of international communication and industrial testing field,optical fiber cables are often in harsh working environments with high temperature, high humidity and high pressure, and will be used in deep-sea signal transmission, urban communication network construction, petrochemical smelting, national defense and military industries. Its application environment puts forward higher and higher requirements for optical fiber strength. The strength of conventional silica fiber can not meet the requirements of harsh environments, which restricts the further expansion of its market application range. Theoretically, using the bond length and surface energy between fused silica atoms, it can be calculated that the theoretical maximum breaking force of standard single-mode fiber is 203 N, while the average breaking force of commercial single-mode fiber is 47.6 N, which is far less than the theoretical maximum breaking force. The main reason is that during the optical fiber manufacturing process, it can inevitably experience the thermal and cold changes of high-temperature fused silica to accumulate internal stress inside the optical fiber. All will cause micro-cracks on the surface of the fiber, reducing the strength of the fiber. Therefore, suppressing the micro-cracks on the surface of the optical fiber and effectively improving the strength of the silica fiber have become the key exploratory areas by researchers. This article uses the passive single-mode quartz preform provided by Zhongtian Technology Co., Ltd(diameter 35 mm, core NA 0.14). The experiment is designed by an online active temperature-controlled annealing furnace to reduce the temperature difference between the surface temperature and room temperature when the fiber is released from the furnace, eliminate the internal stress of the fiber and inhibit the generation of micro-cracks on the surface and inside of the fiber. The newly installed online active temperature control annealing furnace has a length of 600 mm, and the furnace body has built-in three-stage heating wire, which can realize the temperature adjustment of 0~600 ℃ inside the furnace body. Acrylate was used as the coating material, and the fiber was drawled online by UV curing. The fiber cladding diameter was 125±1 μm, the coating diameter was 245±5 μm, and the coating/cladding concentricity error was less than 10.0 μm. The breaking force of the optical fiber is the reference standard to measure the strength of the optical fiber. According to international standard, the average breaking force of optical fiber is tested by universal tensile testing machine. The running speed of the tensile testing machine was 50 mm/min, and 15 samples were selected for each set of tests, and the length of each sample was 1 m. Different preform pretreatment processes,drawing speeds and active temperature control annealing processes are measured in experiment. The surface morphology of preforms and fibers with different treating conditions were characterized by reflective optical microscope (OLYMPUS, BX53M) and Scanning Electron Microscopy(SEM,ZEISS-EVO-18). The influencing factors of optical fiber breaking force were analyzed and studied. The result shows that average breaking force of the fiber behaves a downward trend with the increasing of drawing speed. Through the analysis of the fracture curve of the optical fiber Weibull function under different process conditions, with the optimization of the process conditions, the tensile force of the optical fiber increases but the sample consistency deteriorates. The micro-cracks on the surface of optical fibers and preforms can be effectively suppressed and average fiber breaking force was increased from 36.69 N without any treatment to 68.28 N, and the breaking force increased by 86%, through flame polishing and gradient cooling treatment on preforms, optimizing the active temperature control annealing process and decreasing the drawing speed. Relevant experimental surfaces carried out flame polishing pretreatment on the preform and optimization of the annealing process during the drawing process, while reducing the fiber drawing speed, which can effectively improve the average breaking force of the fiber. The research has opened up a wider application space for high-strength optical fibers in harsh environments such as oil exploration, submarine optical cable laying, and climate monitoring.