Polyurethane rigid foams, constitute %23 of total PU industry, can be produced from petroleum products with low thermal conductivity, high mechanical properties and good aging performance. Closed cell content and their cell size distribution has huge impact for energy efficiency of household refrigerators. Increasing homogeneity of cell content and cell size directly increase the thermal performance of rigid PU foam. In order to achieve this, nanoclays (montmorillonite MMT),carbon nanotubes,carbon nanofibres are widely used for cell size reduction with nucleation effect and also improving hardness, toughness, stiff-ness and mold shrinkage on the foam.However ; because of hydrophilicilty of MMT can easily agglomerated in hydrophobic polyol mixture. In order to increase dispersibility of MMT, ıt should modify wtih organic modifiers. In the present study, to increase dispersibility of MMT, nanocrystalline cellulose (NCC) was used because NCC does not agglomerate in polyol mixture and nanocrystalline cellulose , is typically a rigid rod cellulose domain with 1-100 nm in diameter and tends to hundreds of nanometers in length and also it has very large surface area. Low densitycrystalline nanocellulose was obtained from cotton linter ( from Şanlıurfa – Turkey) via pulping, bleaching, acid hydrolysis, neutralization and lyophilization to increase the degree of crystallinity of NCC.MMT was taken from Eczacıbaşı ESAN.In the procedure, %0,03 NCC-%1 MMT wt.added to polyol mixture and high shear mixer (20000 rpm) was used to get a better mixture. Then, iscyanate and polyol were poured to mould. The resulting polyurethane was characterized by SEM (Scanning electron microscope), thermal conductivity, mechanical strength, TGA (Thermogravimetric analysis), DSC (differential scanning calometric) tests. The results showed that %0,03 NCC-%1 MMT reduce thermal conductivity 0,5mW/mK and improving 20kPa mechanical strength of final polyurethane than usage %1wt MMT by itself.