This pepar studied pyruvate dehydrogenase using dynamic light scattering (DLS) with photon counting technique and obtained some data on its microstructure. Radii of PDO and E2-X-K are measured. It is found that at lower concentration the aggregation can be neglected, the size distribution is monodispersion, and the linewidths of DLS spectra of PDC and E2-X-K are proportional to q2 and q3 respectively. But at higher concentration the size distribution is polydispers ion and Γ is proportional to qα, where a is fractional.