  In this paper, we study the generation of entanglement in a double-$\Lambda $
system. Employing standard method of laser theory, we deduce the dynamic
evolution equation of the two-mode field. We analyze the available entanglement
criterion for double-$\Lambda $ system and the condition of entanglement
existence. Our results show that under proper parameters, the two-mode field
can entangled and amlified.
