We use the separation of variable treatment to treat some time-dependent sy
stems, and point out that the condition of separability is the same as the
condition of existence of invariant, and the separation of variable treatme
nt is interrelated with the quantum-invariant method and the propagator met
hod. We directly use the separation of variable treatment to obtain the wav
efunctions of the time-dependent Coulomb potential and the time-dependent H
ulthen potential.