Electron cloud effect is studied at Fermilab. Effort was made to measure SEY conditioning effect at Main Injector. E-cloud simulation code POSINST was used to study the generation of E-cloud. Yuri Alexahin brought collaboration with the eRHIC group to study e-cloud relate problem at eRHIC. This talk will focus on SEY in-situ measurement test stand and simulation result and their application to BNL eRHIC.