This invention relates to a polysiloxane-based compound and a solid polymer electrolyte composition prepared using the same. More particularly, the present invention relates to a polysiloxane-based polymer, which promotes easy cross-linking and also enables to control the level of cross-linking according to the concentration of an acryl group by introducing a polyalkyleneoxide group and an acryl group are introduced as side chains to the backbone of methylsiloxane polymer.