In order to obtain crosslinking reagent with hign molecular weight, acrolein was polymerized by radical process. The aldehyde group in acrolein monomer is stable and not hydrated even in aqueous solution without catalyzer. But after the polymerization by radical process, aldehyde group in acrolein can be easily raised to activated state and forms aldehydehydrate ether linkage, which is chemically inactive. White powdery polyacrolein obtained by radical process in aqueous solution was chemically inactive and did not melt, and did not dissolve in any organic solvents at room temperature, except in pyridine aqueous solution. However this polymer dissolved in NaOH aqueous solution and SO2 aqueous solution, to form derivatives. It may be concluded from the above results, that polyacrolein, polymerized in aqueous solution, is not suitable to the crosslinking reagent of celullose. Other method should be adopted to gain chemically reactive polyacrolein.While, acrolein was polymerized in alcohol solution by radical process, to produce transparent block which was soluble in dioxane, DMF and DMSO at room temperature, but insoluble in 12% SO2 aqueous solution. Aldehyde groups in transparent block are acetalyzed to form unstable hemiacetal linkages, and several days after the polymerization, this resulting colorless transparent block became brown and brittle.