Based on DSSCMM, this paper puts forward the method and process of evaluating the maturity of data sovereignty security capability , and puts forward some suggestions to improve the weakness of our country's data sovereignty security capability.Construct and use marginal sampling method to determine effective samples, apply expert investigation method to determine the weight of capability dimension, and use sample scoring method to calculate the scores of capability dimensions, then determine the key process area score and data sovereignty security capability score.The capacity maturity of data localization, cross-border data flow and data extraterritorial jurisdiction has reached a higher level, but the capacity maturity of data extraterritorial jurisdiction actually tends to be necessary level, and the data sovereignty security capacity maturity of our country has reached a sufficient level.In order to improve the maturity of our country's data sovereignty security capability, it is suggested that we should start from "culture and education" and "technical tools" of data local storage and data cross-border flow.Particular attention shall be paid to the timely application of the long-arm jurisdiction of the Data Security Law in extraterritorial judicial activities, and guide and promote the application of independent technology products in the domestic network ecosystem.