Abstract: Collapsible loess, as a common problem soil in Northwest China, has brought great challenges to civil engineering construction in Northwest China. How to reduce the collapsibility of loess at low cost is an urgent problem to be solved by the engineering community. Taking an irrigation canal in Shaanxi Province as the engineering background, the improvement effect of nano clay on collapsible loess was analyzed by combining indoor and outdoor tests. The indoor test results show that with the increase of nano clay content, the liquid limit, plastic limit and plastic index of the modified loess increase, and the optimum moisture content of the modified loess increases with the increase of nano clay content, which has important engineering significance for the construction of collapsible loess areas. Two kinds of strength tests show that nano clay can improve the strength of modified loess to a certain extent. The dispersity and collapsibility of modified loess were decreased by adding nano clay. In addition, an outdoor test was carried out in the canal site. The test results showed that the stability of loess was significantly improved after adding 2.0% nano clay. The outdoor test results are basically consistent with the indoor test results. This study provides a new method for eliminating collapsibility in loess area, and provides a useful reference for similar projects in the future.