The invention discloses a crucial boiler pipeline online measurement system. The crucial boiler pipeline online measurement system comprises two obviously-identified radial deformation measurement metal blocks, a radial measurement binocular camera, two obviously-identified axial deformation measurement metal blocks, an axial measurement binocular camera, a displacement sensor and at least one stress and strain transducer, wherein the stress and strain transducers are arranged at the bottoms of the metal blocks. The displacement sensor is positioned between two prearranged axial deformation measurement metal blocks, and two sensing heads contact with the metal blocks respectively. The binocular cameras are connected with an industrial switch and are connected to a main control machine via a transmitting network bridge and a receiving network bridge. The crucial boiler pipeline online measurement system is capable of detecting data such as stress, strain and displacement of a boiler pipeline comprehensively and efficiently in real time to reflect boiler pipeline damage degree, and is used for judging remaining life of the boiler pipeline to perform failure early warning, so that safety and stable operation of electric power are guaranteed.