Filters for soft-x-ray are mostly self-supported metal thin films. Under experimental circumstance, while long exposure to the air of the self-supported metal thin film, impurity atoms will enter into self-supported thin film, which will result in decline of self-supported thin film′s optics performance. Zr filters have high transmittance at band from 5 nm to 20 nm because of its low mass absorption coefficient and density. After vapor depositing NaCl film on cleaned float glass as a release agent, Zr film was sputtered on NaCl film. Self-supported Zr film wass prepared after NaCl film being dissolved in deionized water. To prevent surface oxidizing and impurity atoms from the air entering Zr film in experimental environment, C or Si film with 10 nanometer thickness was sputtered on both Zr film sides for separating Zr from the air. Measurement result of C/Zr/C and Si/Zr/Si film shows that C or Si film has little influence on self-supported Zr film performance.