The Hamiltonian operator of a system of Ξ-type three-level atomic Bose-Einstein condensate interacting with single-mode squeezed coherent light field is improved in terms of the lattice-liquid model, and the squeezing properties of light field in this system are studied. The results show that two quadrature components of light can be squeezed periodically. The maximum depth of squeezing is determined by the interaction intensity between light field and atoms and the initial squeezing factor of light, and squeezing period is correlated with the frequency of the light field.