Quantum Search Algorithm made a big impact by being able to solve the search problem for a set with $N$ elements using only $O(\sqrt{N})$ steps. Unfortunately, it is impossible to reduce the order of the complexity of this problem, however, it is possible to make improvements by a constant factor. In this paper we pursued such improvements for search problem in sets with known probability distributions. We have shown that by using a modified version of quantum search algorithm, it is possible to decrease the expected number of iterations for such sets.