Circular Electron Position Collider (CEPC) is proposed as a Higgs or Z factory. One option of CEPC-ECAL(Electromagnetic calorimeter), designed based on the Particles Flow Algorithm(PFA), consists of tungsten and scintillator coupling with SiPM as active sensor. A advanced study of the gain with single photon and the responding curve of SiPM will be presented. Scintillator module also had be studied, different degrees of polishing and different ways of coupling with SiPM, to make light yield meet the dynamic range requirements and improve the uniformity of output light. A 20𝑐𝑚×20𝑐𝑚 single layer prototype had be produced and the cosmic-ray test results also will be presented.