Zainab Ayati - Department of Engineering sciences, Faculty of Technology and Engineering East of Guilan, University of Guilan, P.C. ۴۴۸۹۱-۶۳۱۵۷, Rudsar-Vajargah, Iran
Roxana Asayesh - Department of Mathematics, Faculty of Mathematical Sciences, University of Guilan Rasht,Iran
Farideh Salehi - Department of Mathematics, Darab Branch, Islamic Azad University Darab,Iran

Many important phenomena in various fields are described and generalized by a fractional partial differential equation.In this paper, the modified simple equation method which is widely applicable to handle nonlinear wave equations, is successfully implemented for constructing exact solutions of two nonlinear fractional equations, namely the space-time nonlinear fractional potential Kadomstev- Petviashvili (PKP) and Sharma-Tasso- Olver (STO) equations in the sense of the modified Riemann-Liouville derivative. As a result, some new exact solutions are successfully obtained for them

Modified simple equation method, Space-time nonlinear fractional differential equation, Exact solution