Monopterus albus is highly susceptible to spoilage due to high protein and moisture contents while frozen storage can effectively prolong the shelf-life. To study the effect of liquid nitrogen freezing (LNF) on quality, microstructure of ice crystal and muscle fiber, and physicochemical properties of proteins, Monopterus albus was frozen at -20°C by refrigerator (RF, control), -50°C, -80°C, and -110°C by LNF, respectively. The -110°C LNF exhibited the highest freezing rate among four groups, contributing to the formation of small ice crystals with more uniform distribution and alleviating the damage to muscle fiber. In -110°C LNF group, protein secondary structure changed relatively subtle, resulting in high protein solubility, Ca2+-ATPase activity, and total sulfhydryl content, as well as low surface hydrophobicity and disulfide bond content. LNF retarded the rise of TVB-N value, prevented the loss of immobilized and free water, and maintained water holding capacity and shear force. In conclusion, -110°C LNF was recommended a promising freezing process for frozen Monopterus albus due to less alteration of quality and alleviation of protein denaturation.