Diatomite is a porous material formed by the remains of diatom, which has the advantages of large specific surface area, good corrosion resistance, green and innocuity. Diatomite-based materials as adsorbent or photocatalyst show wide application prospects in sewage treatment because of easily available raw material and low in price. However, most of the natural diatomite contains some metal oxide impurities, which may reduce the porosity and affect the adsorption and photocatalysis performance of diatomite. Therefore, the majority of research of diatomite materials for water treatment have been focused on surface decoration and composite modification to strengthen the adsorption and photocatalytic performance. In this review, the recent research progress of diatomite-based materials in treatment of wastewater(such as organic wastewater, eutrophic wastewater, heavy metal ion wastewater, etc.) are summarized and commented based on the principle of adsorption and photocatalysis, and the relationships between structure and performance of diatomite are analyzed from different modification methods. Finally, suggestions and outlooks on the future research directions in diatomite-based materials as adsorbent or photocatalyst are given.