In this paper, we consider the existence of the solution for the biharmonic
eigenvalue problem under Navier boundary condition
Δ2u=λa(x)u+f(x, u), x∈ Ω,
u=Δu=0, x∈ Ω,
where Ω is a bounded domain in RN(N ≥ 5), Δ2 is the biharmonic operator, and the weight function a(x) ∈Lr(Ω)(r ≥ N/4) with a(x)> 0 a.e. in Ω. By variational method, we obtain the second eigenvalue of this problem when f(x, u)=0 and study the structure of it, and discuss the existence of the nonzero solutions under resonance and nonresonance conditions.