A negotiation processing method for a security algorithm, comprising: selecting, by a first control network element attached by a first UE and a second control network element attached by a second UE, according to a security capability of the first UE and a security capability of the second UE, a security algorithm supported by both the first UE and the second UE; and notifying, by the first and second control network elements (21, 22), the selected security algorithm to the first UE and the second UE, wherein the selecting, by the first and second control network elements (21, 22) according to the security capability of the first UE and the security capability of the second UE, the security algorithm supported by both the first UE and the second UE comprises: randomly selecting from an intersection of a security algorithm supported by the first UE and comprised in the security capability of the first UE and a security algorithm supported by the second UE and comprised in the security capability of the second UE, one security algorithm as the security algorithm supported by both the first UE and the second UE; or selecting, by the first control network element, according to an intersection of a preconfigured security algorithm priority list and a security algorithm that is supported by the first UE, a first ordered algorithms list corresponding to the first UE, selecting, by the second control network element, according to an intersection of the security algorithm priority list and a security algorithm that is supported by the second UE, a second ordered algorithms list corresponding to the second UE, and selecting, by the second control network element, from an intersection of the first ordered algorithms list and the second ordered algorithms list by using an algorithm selection policy, the security algorithm supported by both the first UE and the second UE. selecting, by a first control network element attached by a first UE and a second control network element attached by a second UE, according to a security capability of the first UE and a security capability of the second UE, a security algorithm supported by both the first UE and the second UE; and notifying, by the first and second control network elements (21, 22), the selected security algorithm to the first UE and the second UE, wherein the selecting, by the first and second control network elements (21, 22) according to the security capability of the first UE and the security capability of the second UE, the security algorithm supported by both the first UE and the second UE comprises: randomly selecting from an intersection of a security algorithm supported by the first UE and comprised in the security capability of the first UE and a security algorithm supported by the second UE and comprised in the security capability of the second UE, one security algorithm as the security algorithm supported by both the first UE and the second UE; or selecting, by the first control network element, according to an intersection of a preconfigured security algorithm priority list and a security algorithm that is supported by the first UE, a first ordered algorithms list corresponding to the first UE, selecting, by the second control network element, according to an intersection of the security algorithm priority list and a security algorithm that is supported by the second UE, a second ordered algorithms list corresponding to the second UE, and selecting, by the second control network element, from an intersection of the first ordered algorithms list and the second ordered algorithms list by using an algorithm selection policy, the security algorithm supported by both the first UE and the second UE. randomly selecting from an intersection of a security algorithm supported by the first UE and comprised in the security capability of the first UE and a security algorithm supported by the second UE and comprised in the security capability of the second UE, one security algorithm as the security algorithm supported by both the first UE and the second UE; or selecting, by the first control network element, according to an intersection of a preconfigured security algorithm priority list and a security algorithm that is supported by the first UE, a first ordered algorithms list corresponding to the first UE, selecting, by the second control network element, according to an intersection of the security algorithm priority list and a security algorithm that is supported by the second UE, a second ordered algorithms list corresponding to the second UE, and selecting, by the second control network element, from an intersection of the first ordered algorithms list and the second ordered algorithms list by using an algorithm selection policy, the security algorithm supported by both the first UE and the second UE.