H4 thin films (which is a compound of titanium oxide and lanthanum oxide，chemical formula is LaTiO3) have been prepared by the ion assisted electron beam depositing technology. The effect of the substrate temperature and oxygen gas stress influencing on the optical characteristics of H4 thin films have been investigated.It is found that the refractive index n dramatically increases with the substrate temperature building-up，the value of n808 nm is 2.14 at 100 ℃ of the substrate temperature; the extinction coefficient k has changed little with the oxygen pressure reduction, the value of k400 nm is 2×10-4 at 2.67×10-2 Pa of the oxygen pressure. The optimized parameters are applied to the preparation of high reflection mirror of 808 nm lasers, compared with the lasers using titanium oxide as HR films, have obtained a little better laser output characteristics. Therefore, it is a kind of new method of completely feasible that H4 thin films are used as high reflectivity facet coatings of laser diodes.