A water-soluble polymer dispersion, process for producing the same and a method of use therefor. In particular, the water-soluble polymer dispersion is one comprising water-soluble polymer fine particles of 100 .mu.m or less diameter having at least one ionic property selected from among cationic, amphoteric, nonionic and anionic properties together with a polyalkyleneimine and/or a product of polyalkyleneimine modification wherein according to necessity an appropriate amount of water-soluble inorganic salt is incorporated. The provided process enables easily performing the production in dispersed form by means of production facilities of low cost. The obtained water-soluble polymer dispersion is excellent in storage stability and exhibits satisfactory fluidity and solubility so as to enable use in papermaking raw material pretreatments added to papermaking raw materials prior to machine operation and also for enhancement of freeness, increase of sizing degree and enhancement of yield. Further use can be found in incorporation in an organic sludge or paper mill sludge for flocculation and ensuing drainage.