Considering that the equilateral triangle structure of H3- cluster can be formed from the interaction of H- with two hydrogen atoms, a modified arrangement channel quantum mechanics method has been used to calculate the total energy curve for this structure. The result shows that the curve has a minimal energy -1.6672 a.u. at an internuclear distance of 1.77a0, so its dissociation energy (binding energy) is D(H- + H+ H) = 0.1395 a.u. This means that the cluster H3- may be formed in an equilateral triangle structure with a bond length of 1.77a0.