Welcome everyone to attend the International Conference on Nonlinear Science and Complexity, Budapest, Hungary, August 6-11, 2012. Thank all of you to submit your recent researches to DVC2009 for exchanging ideas. The First Conference on Nonlinear Science and complexity was held in 2006 at Beijing, China. The Second Conference was held in 2008 at Porto, Portugal. The third Conference was hold in 2010 at Ankara, Turkey. This conference provides a place to exchange recent developments, discoveries and progresses on Nonlinear Science and Complexity. The aims of the conference are to present the fundamental and frontier theories and techniques for modern science and technology, and to stimulate more research interest for exploration of nonlinear science and complexity. The conference will focus on fundamental theories and principles, analytical and symbolic approaches, computational techniques in nonlinear physical science and nonlinear mathematics. Topics include but not limited to • Chaotic Dynamics and Transport in Classic and Quantum Systems • Complexity and Nonlinearity in Molecular Dynamics and Nano-Science • Complexity and Fractals in Nonlinear Biological Physics and Social Systems • Lie Group Analysis and Applications in Nonlinear Science • Nonlinear Hydrodynamics and Turbulence • Bifurcation and Stability in Nonlinear Dynamic Systems • Nonlinear Oscillations and Control with Applications • Celestial Physics and Deep Space Exploration • Nonlinear Mechanics and Nonlinear Structural Dynamics • Non-smooth Systems and Hybrid Systems • Fractional dynamical systems.