The dynamical behavior of entanglement for excitonsi in two quantum dots placed in a caivty driven by a broadband squeezed vacuum is studied in the low exciton density regime. It is found that the excitions in two quantum dost can evole into a pure entangled state only when the dissipaion of the caivity and exction modes is negligible. When the injected field into the cavity is a squeezed vacuum, the exctions will be in a two-mode Gaussian entangled mixed state even in the long time limit. Analytical expressions are derived, showing the dependece of the entanglement property of the excitons in two quantum dost on the squeezing properties of th inital state prepared in the cavity and the strength of two-photon correlations of the squeezedvacuum injected into the cavity.