Recently, the mechanochromic materials, which can detect the mechanical force by changing optical properties, have invoked extensive interest. These materials can make use of mechanical energy to facilitate the transformation of the chemical or physical structures of polymer chains, so they have great application value in the fields of force sensing, self-healing materials and so on. In this review, we summarize the recent development of the mechanochromic polymer and discuss their preparation methods in detail. The first method involves the physical blending of a dye into a polymer matrix. When the polymer matrix deforms under stress, the macroscopic aggregated dye molecules will be dispersed which exhibits different optical properties. The second method refers to the covalent linking of a mechanophore to a polymer backbone or side chains. The mechanical stimulus induces the selective chemical transformation of the mechanophore at atomic scale and leads to the change of optical properties. Finally, we review the current problems faced by this kind of functional polymer and prospect the future development.