Gilad Gour and Nolan R Wallach [J.Math.Phys.51 112201 (2010)] have proposed the 4-tangle and the square of the I concurrence.They also gave the relationship between the 4-tangle and the square of the I concurrence.In this paper,we give the expression of the square of the I concurrence and the n-tangle for six-qubit and eight-qubit by some local unitary transformation invariant.We prove that in six-qubit and eight-qubit states there exist strict monogamy laws for quantum correlations.We elucidate the relations between the square of the I concurrence and the n-tangle for six-qubit and eight-qubits.Especially,using this conclusion,we can show that 4-uniform states do not exist for eight-qubit states.