The conditional Lie B(a)cklund symmetry method,as a generalization of the conditional symmetry and Lie B(a)cklund symmetry methods,is developed to study the Hamilton-Jacobi equations.It is shown that the equation ut=u x+1 n +B(u)ux+C(u)admits a class of conditional Lie B(a)cklund symmetry for certain functions B(u) and C(u).As a result,a complete description of structure of solutions to the resulting equations associated to the conditional Lie B(a)cklund symmetry is performed.