With the rapid development of modern science and technology, the demand for expanding the service conditions of materials has become increasingly intense. The mechanical/physical properties of materials under diverse and wide-range extreme conditions have become a core issue of concern in various fields, and there is an urgent need to establish the ability to predict the performance of materials under such conditions. Focusing on the major needs of the country, aiming at the advanced materials and structures that have a wide application prospect in national strategic equipment, focusing on their mechanical behavior, strength theory and characterization methods under diverse and wide-range extreme conditions, the author originally proposed a method that could quantitatively characterize the effect of temperature on the mechanical/physical properties of materials - the Force-Heat Equivalence Energy Density Principle (Li’s principle of energy equivalence). Based on this principle, for the first time, established a series of theoretical quantitative characterization models for the mechanical/physical properties (fracture strength, yield strength, ultimate strength, fatigue strength, creep life, buckling strength, hardness, melting point, band gap width, electrical breakdown strength, and exciton energy, etc.) of various material systems, including inorganic non-metallic, metallic, polymeric, and composite materials, without any fitting parameters.