In this work, strongly hydrophilic ionic liquid (IL) was introduced into the metal organic frameworks (MOFs) by the solvent-assisted linker exchange (SALE) method. Low humidity sensors based on IL functionalized MOF-801 materials were prepared. The as-prepared sensor shows a high response of 20.3 (in the humidity range of 0% RH to 35% RH, 0 ppmv to 8138 ppmv), small hysteresis (~1% RH) and good long-term stability (>100 days). In particular, the optimized sensor shows fast response (~400 ms) and high resolution (1% RH). This work provides a potential humidity sensitive material for preparing high performance low humidity sensors.