Wang, L. Benwell, A.L. Brachmann, A. Colocho, W.S. Decker, F.-J. Huang, Z. Maxwell, T.J. Tao, T. Turner, J.L. TUP070 linac timing experiment operation simulation 2015 2015-12 The energy jitters of the electron beam can affects the FEL in self-seeded modes if the jitter is large compared to the FEL parameter. We work in multiple ways to reduce the jitters, including hardware improvement, optimization linac set-up. This paper discusses the optimization of linac set-up. The solutions always suggest that we can largely reduce the energy jitter from a weak compression at BC1 and a stronger compression at BC2. Meanwhile a low beam energy at BC2 also reduce the energy jitter, which is confirmed by the experiment. The results can be explained by a simple model. Experimental results are also presented, demonstrating better than 20% and 40% relative energy jitter reduction for 13.6 and 4 GeV linac operation, respectively.