Gromov-Witten invariants, in certain situations, count the number of nodal curves on smooth variety with given conditions. It is in general a rational number. On Calabi-Yau threefold, there are two set of integral invariants. The first, called the Gopakumar-Vafa invariants, was introduced in theoretical physics as new topological invariants on Calabi-Yau threefolds, counting the numbers of BPS states. The second is the quantum K-theory, a K-theoretic variant of the Gromov-Witten theory. On genus 0, we proved that two invariants are related by linear relations. This is a joint work with Yuan-Pin Lee. If time permitted, I will discuss the higher genus case and their relation with multiple cover formula.