The nonlinear stability of Kiewitt-Lamella single-layer reticulated shells is analyzed by means of random imperfection modal method,and the stable ultimate load of the reticulated shell structure,which is affected by both the spatial sample number of random defect and the rise-span ratio,is investigated.Then,a comparison of calcu- lated results is made between random imperfection modal method and consistent imperfection modal method.The results show that (1) the spatial sample number of random defect should be not less than 90 for the stability analy- sis of structures via statistical method; (2) for the reticulated shell structure with large rise-span ratio,the probabi- listic reliability to calculate the critical load via consistent imperfection modal method is rather low,so that it is nece- ssary to verify the critical load with the help of random imperfection modal method; and (3) when the rise-span ra- tio of a single-layer reticulated shell is less than 1/6,the calculated stable bearing capacities obtained by the two a- bove-mentioned initial defect distribution methods are nearly equal.