  As an analogy to Gopakumar-Vafa conjecture on CY 3-folds, Klemm-Pandharipande
defined GV type invariants on CY 4-folds using GW theory and conjectured their
integrality. In this paper, we define stable pair type invariants on CY 4-folds
and use them to interpret these GV type invariants. Examples are computed for
both compact and non-compact CY 4-folds to support our conjectures.
