The invention discloses a multispectral optical technology fused temperature measuring device. The temperature measuring device comprises a multispectral tunable laser device, a variable color filter,a light beam shaping device, a light beam bidirectional beam splitter, a reference arm, a spectrograph, a collimation and beam expanding lens assembly, a pinhole diaphragm, a high-velocity scanning galvanometer, a large-aperture microobjective, a water channel, an ultrasonic detector, a high-precision temperature heating controller, a temperature sensor and a computing unit. According to the device, internal temperature distribution condition of tissues for tumor local thermotherapy can be measured comprehensively and quickly in real time, imaging and accurate measurement can be carried out simultaneously on changed feature information of internal fine morphological structures of the tissues in the heating process, and rapid multi-dimensional imaging is provided in the state that the internal structures and components inside the tissues are changed in tumor thermotherapy.