MgO carbonization technology was used to solidify the dredged sediment. The main influencing factors and micro-mechanism of reactive MgO carbonization solidification of sediment were systematically analyzed through strength tests and microscopic characteristic tests. The results indicate that more hydration products and carbonization products can be generated with the increase of reactive MgO content， and the strength of sediment increases significantly. The water content and compaction degree are two main factors that affect the transport of CO₂ in soil， and the increase of both will lead to the decrease of CO₂ absorption， thus affecting the carbonization and solidification effect of sediment. The long-term carbonization can cause some carbonization products to undergo metamorphic reaction， so the strength of sediment increases first and then decreases with the increase of carbonization time. The encapsulation， cementation and pore filling of soil particles by hydration products and carbonization products are the main mechanism of reactive MgO carbonization solidification of sediment.