Abstract: The mechanical degradation by high-speed stirring of poly (ethylene oxide) and polyacrylamide in aqueous solution were studied. The limiting chain length and the rate constant of degradation were shown to change with concentration, and the rate constant was shown to be related to stirring time at any given concentration. The dependence of the number of scission per molecule on stirring time can be expressed by the following equation According to the experimental result, it was inferred that molecules of neither polymer acquire the entanglement structure at a concentration of 0.5%.As shown by gel permeation chromatogram comparing the original and the degraded polymers, the molecular weight distribution of the latter became narrower.