In this paper, we gave a theoretical analysis to the cycle-length of cocoon filament in the raw silk by mixed cocoon reeling, which correlate closely to the size dynamic process in the raw silk reeling with fixed number of cocoons.

the distribution of the cycle-length of cocoon filament, the continuous property of raw silk size, the distribution of the cocoon number of different cocoon layers in silk filament, the eigenvalue of cocoon size.