Abstract: In view of the varied weft density of sparse-dense fabric,a sectional input of the weft distribution information is presented.The method first introduces the conception of simple weft distribution section in which the change pattern of weft density is simple,definite and can be predefined,and further divides a weft density variation unit into several simple weft distribution sections,thus solving the input problem of the information concerning the varied weft density.According to the above method,a software program is worked out,by which the desired weft distribution pattern of the fabric can be input into the loom control system.Several commonly used weft density variation rules are predefined,and the expression for each rule is given.Moreover,the weft density function which varies as the length within the range of a prescribed length of fabric is constructed,and the algorithm of determining the take-up value for each weft yarn according to the weft density function is given.