Low humidity detection has always been a challenge in the field of humidity detection. Humidity sensors base on ionic liquid modified metal organic frameworks (MOFs) derived polymer films were prepared in this work. The ionic liquid ligand was uniformly introduced in the frameworks of UIO-66 to enhance the hydrophilicity of sensing materials, the caused defects sites are beneficial for adsorption and desorption, and the MOFs based functional films were easily obtained by in situ photoinduced thiol-ene click reaction. The obtained humidity sensor exhibits a linear response in low relative humidity (RH) range (5% RH - 30% RH) with a tiny humidity hysteresis (~0.2% RH) and short response time to humidity change (response/recovery time is 0.6 s/1.7 s, respectively).