We investigate graded K-theory for Leavitt path algebras. There is a tight connection between the algebraic structure of Leavitt path algebras and the positive cone of the graded Grothendieck group of Leavitt path algebras. We found there is a certain quotient of algebraic filtered K-theory which is a graded invariant for Leavitt path algebras. This is a joint work with P. Ara and R. Hazrat.