<p>Organic substances such as fibroin, collagen, and cellulose are vital components of organic cultural heritages, carrying significant ancient cultural information. However, their sensitivity to environmental factors leads to heritage deterioration and reduction of values. This review briefly introduces the composition of several major organic cultural heritages (silk fabrics, leather, parchment, paper, and wood), focusing on their multilayer structure of the molecules. All aspects of organic heritages are evaluated from surface to interior using modern analytical techniques. Furthermore, the review covers the different deterioration mechanisms of organic cultural heritages by temperature, humidity, light, air pollutants, and microorganisms. Hydrolysis and oxidation are the main deterioration formats during all types of cultural heritages. The original degradation of silk fabrics and paper took place in the amorphous region, while both the crystalline and amorphous regions are destroyed as aging progresses. Compared to silk fabrics, leather and parchment are more prone to suffer bio-deterioration due to the weakness of the covalent bonds between the tanning agent and collagen. Compared to traditional contact conservation methods, contactless methods provide protection while avoiding damage to the fragile and precious organic heritages, which promotes the development of biopolymer-based composites as a promising alternative. In conclusion, it describes potential challenges and prospects for the appropriate conservation of organic cultural heritages. The comprehensive exploration of organic cultural heritages from a modern perspective is expected to promote its preservation and the transmission of history and culture.</p><p></p>