The collapsibility of loess has exerted adverse impact on the stability of tower base of electric power transmission line in Henan Province.In view of this,we conducted tests on the basic physical properties and collapsibility of loess in Sanmenxia area in Henan Province in order to obtain collapsibility coefficient and evaluate collapsibility grades.Moreover,by analyzing the effects of changing vertical pressure and initial water content on loess collapsibility,we examined the relationship between collapsibility and structural strength of loess.Test results show that the relationship between vertical pressure and collapsibility coefficient is not a simply and monotonically increasing function; instead,we found intervals of vertical pressure which induces the exacerbation or weakening of collapsibility.A plastic limit of 18.6% is the dividing point on collapsibility curve which means that collapsibility weakens when initial water content is close to or over the plastic limit,or exacerbates when initial water content is smaller than that plastic limit.In addition,the relationship between water content and collapsibility coefficient is also not a simple and monotonically decreasing function where the turning point on that function would appear when initial water content equals 10% and structural strength is 200 kPa at the same time.