A method for generation of Ncs set is disclosed as: an upper limit value Ncs_max of Ncs is determined firstly, Ncs values which are less than or equal to the Ncs_max are selected to be elements of an initial Ncs set, a screening Ncs set is generated from the initial Ncs set, and then a final Ncs set is generated from the screening Ncs set. The final Ncs set can satisfy the maximal covering demand of the system, and when a random access preamble is generated by cyclic shift amount contained in the final Ncs set, the interference between and in cells can be decreased.