Ferroelectric　nanostructures　have　recently　attracted　much　attention　due　to　the　continuous　demand　of　miniaturizing　devices　and　discovering　novel　phenomena.　Therefore,　in　depth　study　of　the　ferroelectric,　and　dielectric　properties　at　various　particle　sizes　in　nanoscale　ferroelectrics　is　of　technological　importance.　Unfortunately,　research　aimed　at　discovering　and　understanding　the　size　effect　on　the　electric　properties　of　ferroelectric　nanostructures　are　scarce.　Here,　we　investigate　the　spontaneous　polarization　and　dielectric　constant　at　various　sizes　of　nanocrystalline　potassium　niobates　(KNbO3)　by　using　powder　X-ray　diffraction　(XRD)　Rietveld　refinement,　Raman　spectroscopy,　and　theoretical　calculation.　It　is　surprising　to　find　that　the　spontaneous　polarization　P-s　reaches　the　highest　value　of　40.3　mu　C　m(-2)　at　100　nm,　and　decreases　with　increasing　grain　size　from　100　nm　to　500　nm.　The　dependence　of　the　dielectric　constant　on　the　grain　size　shows　similar　variation　as　that　of　spontaneous　polarization.　It　is　deduced　that　the　large　lattice　distortion　induced　by　lowering　the　grain　size　facilitates　the　increase　of　P-s,　which　in　turn　contributes　mainly　to　the　enhancement　of　the　dielectric　constant.