The notion of Killing-Ricci
forms of Lie triple algebras is introduced as a generalization of both of Killing
forms of Lie algebras and the Ricci forms of the tangent Lie triple systems of
Riemannian symmetric spaces. For a class of Lie triple algebras G, it is shown
that G is decomposed into a direct sum of simple ideals if its Killing-Ricci
form is nondegenerate. As an application, structure of the reductive pair
consisting of a semi-simple Lie algebra and its semi-simple subalgebra is
investigated.