The paper presents a research of the possibilities of an algorithm for MUD, which uses a discrete successive search. The suboptimal methods for MUD in synchronous CDMA systems are prospective class in comparison to the optimal methods, because of the reduced number of calculations and computational complexity. A closed form formula is derived for the number of iteration of the algorithm for obtaining constant error probability. This allows rational use of the computation power of the machine and reduction of the number of the computations in MUD with successive search algorithm.