The results of the theoretical study on RuX^2+(X=O, H, N, C) using density functional method (B3LYP) show that PuO^2+, PuH^2+, PuN^2+ and PuC^2+ can be stable. Ground electronic states are X5^Σ^- (PuO^2+), X8^Σ^-(PuH^2+),X4^Σ^+(PuN^2+) and X9^Σ^-(PuC^2+), and their potential energy functions are in good agreement with the Murrell-Sorbie function, and their force constants and spectroscopic data have been worked out.

Key words: MOLECULAR ION, POTENTIAL ENERGY FUNCTIONS, STABILITY, MECHANICAL PROPETIES