A printing system and control method thereof which insert partitions between printed materials printed by a printing apparatus execute substitution operation in a case that there is no partition. The substitution operation includes executing shift discharge sheet operation which loads printed materials onto a stacker with a shift by units of printed materials to be partitioned, or supplying an partition for substitution from another sheet feed cassette in which partitions for substitution operation are stored, or supplying a sheet from another sheet feed cassette in which other sheets being different from the printed material used to printing of printed materials in at least one of size, type and color as an partition.