For industrially produced C-Mn cryogenic steel, the effects of rare earth Ce additions of 0、6 ug/g、9 ug/g and13 ug/g on the strength and low-temperature toughness of the steel was investigated. Through the tensile experiment and impact experiment, combined with the scanning electron microscope, the fracture morphology-inclusions of the samples with different Ce contents were analyzed and observed. The research results indicated that with the increase of Ce content, the yield strength and tensile strength of C-Mn cryogenic steel increase slowly, while the elongation shows a tendency to increase and then decrease, that is, when the Ce content is 9 ug/g, the strong-plasticity of the product is the best. When the amount of Ce added is 9 ug/g, it obtains the best low temperature toughness, which is mainly attributed to the addition of an appropriate amount of Ce, which effectively modifies the morphology of inclusions, forms fine cotaining Ce inclusions, and enhance fracture resistance in low temperature environment. Moreover, this paper also compares the low temperature toughness at -40℃ of the same specification steel strips with the addition of 9 ug/g (±1 ug/g) Ce and 0 Ce. It is concluded that the impact energy of the steel strip containing 9 ug/g Ce is about 10J higher than that of 0 Ce.