Abstract: In this study,the conformation changes of pectin induced by microwave treatment were determined by intrinsic viscosity,size exclusion chromatography combined with multi-angle laser scattering(SEC-MALLS),as well as dynamic/static light scattering. Results showed that,the intrinsic viscosity of pectin decreased from 4.25 dL/g to 3.35,3.10,2.97 and 2.85 dL/g after microwave treated for 5,15,20,30 min,respectively. The results of SEC-MALLS showed that M_W decreased from 31.38×10⁴ Da to 4.76×10⁴ Da after microwave treated for 30 min,indicating that microwave treatment could lead to degradation of pectin. By analyzing the α values of logarithmic diagram of R_g and M_W of pectin solution,it could be concluded that both origin pectin and microwave treated pectin for 5,15,20 min,the chain conformation of pectin was irregular coil. When the treatment time was extended to 30 min,the chain conformation of pectin molecules became rigid rods. This result was consistent with the conformation change of pectin characterized by dynamic and static light scattering method. This paper provided a theoretical basis for explaining the changes of physicochemical properties of pectin caused by microwave treatment.