The past few years have witnessed the great potential of exploiting channel state information (CSI) retrieved from commodity WiFi devices for contactless human sensing. However, a severe problem hindering practical WiFi sensing applications is that the obtained CSI data contains a large amount of noise, leading to short sensing range and low sensing accuracy. Aiming at solving the critical problem, in this article, we propose to employ a new base signal called CSI ratio to boost the WiFi sensing performance.