D. Molodtsov (1999) [1] introduced the concept of a soft set as a new approach for modeling uncertainties. Xiao et al. [7] and Pei and Miao [8] discussed the relationship between soft sets and information systems. They showed that soft sets are a class of special information systems. So it’s important to study the structures of soft sets for information systems. Shabir and Naz(2011) [20], studied the topological structures of soft sets. In this paper, we continue the study on soft topological spaces and investigate the properties of soft semi-open sets, semi-closed sets, soft semi-interior and soft semi-closure. Then discuss the relationship between soft semi-open (semi-closed) sets, soft semi-interior (semi-closure) and soft open (closed) sets, soft interior (closure) introduced in [20]. We also define and discuss the properties of soft semi-separation axioms which are important for further research on soft topology. These research not only can form the theoretical basis for further applications of topology on soft sets but also lead to the development of information systems.