The paper aims to prepare 850 nm filter that can be used for face recognition by thermal evaporation deposition technique to study the laser damage threshold of the filter and the electric field distribution inside the film. The design and optimization of the 850nm filter was completed by the TFC film system simulation design software. The vacuum box coating machine was used to prepare the filter by adding baffles, adjusting the monitoring wavelength and ion beam assisted thermal evaporation deposition technology. The spectral characteristics of the center wavelength transmittance of 83.05% and the other wavelength bands of T<5% were achieved by the ultraviolet-infrared spectrophotometer test. The laser damage threshold of TiO2/SiO2 combination filter obtained by R-on-1 laser damage test method reached 4.2 J/cm2; and that of ZnS/MgF2 combination filter was 2.8 J/cm2. The air-film interface electric field strength of the TiO2/SiO2 combination filter was 0.3474; and that of the ZnS/MgF2 combination filter was 0.9357. From the microstructure under the microscope, it was found that the ZnS/MgF2 combination film had a larger laser damage spot and was more susceptible to damage than the TiO2/SiO2 combination under the same energy. The narrow band filter can be prepared by adding a baffle and adjusting the monitoring wavelength. In order to obtain a filter film with a higher laser damage threshold, the electric field distribution at the interface between the film and the air is reduced as much as possible when designing the filter, that is, the smaller the electric field intensity distribution at the interface, the more powerful the surface of the film in resistant to laser damage. At the same time, it is found that the laser damage threshold of TiO2/SiO2 combination filter is larger than that of ZnS/MgF2 combination filter.