The problem of polyaniline (PANi) sensor has been poor mechanical and chemical stability under atmosphere condition. In order to overcome these problems, the PANi sensor coated with polyvinylidenefluoride ($PVF_2$) was employed. The morphology of $PVF_2$ coated-PANi layer was showed smooth and transparent properties at 15% concentration of coating solution. The resistance of $PVF_2$ coated-PANi was kept at constant value and had a good stability at long-term periods in presence of humidity.