Based on the theory of density matrix equation for the interaction of light and matter,the characteristics of the population and absorption of a ladd er type three-level Rydberg atom system under the driven of two laser fields ar e investigated.It is found that the variation of the population of Rydberg energ y level with detuning of the probe field is exactly the same as that of the prob e absorption.If the intensity of the probe field is less than that of the coupl ing one,the population of the two levels which associated with the coupling fie ld decreases with the increase of the intensity of the probe field,but the one of the Rydberg level which associated with the probe absorption increases until to equals the population of the intermediate level.Just then,the intensity of the probe and the coupling field is equal.Then,if the intensity of the probe f ield continues to increase,population inversion between the Rydberg and interme diate energy level will appear.This phenomena can be attributed to power broade ning caused by the probe field.Some atoms of the intermediate excited level are pumped to the Rydberg one,and some atoms relax to the ground level quickly.Th us,by adjusting the intensity of the probe and the coupling field,stimulated r adiation can be realized with this Rydberg atomic system.