Tissue substitutes must meet the following conditions: excellent biocompatibility, no toxic reaction, inflammatory reaction, foreign body reaction and allergic reaction, no antigenicity and no carcinogenicity; Biomechanics has certain strength and can bear certain tension and pressure; The chemical properties are stable, and the structure will not change after long-term implantation; Good corrosion resistance, no toxic dissolved substances; Easy to process sculptures, easy to disinfect and so on. Qualified soft or hard materials can be used as tissue substitutes.