The phase behavior of PEB/PES (poly(ethylene-co-styrene)/poly(ethylene-co-butene)) blend system was studied by time resolved laser light scattering with both wide angle and small angle laser light scattering. The phase separation kinetics show that the phase diagram of this system is a closed loop with both lower critical solution transition (LCST) and upper critical solution transition (UCST), which is inconsistent with the results obtained by optical microscope we reported before. All of the phase separation processes including early, middle and late stages have been studied. The coarsening behavior of the blend was characterized in terms of the time change of the maximum intensity I-m, and the magnitude of the scattering vector q(m), at which the intensity becomes maximum. The theory to interpret the phenomena has been studied by many researchers, and it is waiting for further theoretical systematic research. (C) 2010 Elsevier Ltd. All rights reserved.