To obtain polyolefin particles having high degree of porosity, easy in handling, free from dust, and having a narrow mol.wt. distribution by polymerizing an olefin in the presence of a metallocene catalyst in an emulsion.

Ethylene, propylene or a cyclic olefin or their mixture (preferably ethylene or propylene alone) is polymerized in the presence of a metallocene catalyst in an emulsion. A dispersant used in the polymerization is preferably a styrene-diene block binary copolymer or a styrene/diene/styrene block terpolymer. A dispersing solvent is preferably an aliphatic hydrocarbon. The obtained crystalline polymer can be used for obtaining functional compounds such as an epoxide.