By using the ultra-soft pseudo-potential approach of the plane wave based on the density-functional theory, the electronic structures and optical properties of LiF with Li-1 and F+1 vacancies are calculated. The results indicate that: (1) the presence of the vacancy causes defective states within the band gap of LiF; (2) the optical absorption of LiF in the visible-light region is not influenced by the vacancy point-defect (absorption coefficients are still zero); (3) in the ultra-violet region, the weak absorption induced by the Li-1 vacancy, appears within ~99—114nm, and the relatively strong absorption induced by the F+1 vacancy exists in the range of 99—262nm; (4) effects of the Li-1 and F+1 vacancy on reflectivity and loss-function show mainly in the ultra-violet region, which is similar to those of optical absorption.