Let G be a critically 2-line-connected graph and D be the set of vertices with degree two in the graph G. A(G) denotes the maximum degree of G and D≧2k-s(G)={x:(x∈G)(?)(d(x)≥2k-1)}

D2k-1:2k(G)={x:(x∈G)(?)(2k-1≤d(x)≤2k)}

where k is a natural number. The symbol [a] denotes the greatest integer not greater than a. In this paper we prove the following theorems: Theorem 1. Let |D|=α then △ (G)≤2[α/2]; Theorem 2. Let |D|=α and α≥2k≥6

then |D≧2k-1(G)|≤2k[(α-4)/(2k-4)]+2[(α-4-(2k-4)[(α-4)/(2k-4)])/2]; Theorem 3. Let |D|=α and α≥2k≥6

then |D2k-112k(G)|≤2k[(α-4)/(2k-4)]+2[(α-4-(2k-4)[(α-4)/(2k-4)])/2]. And in three theorems above the upper bounds are the best possible.