Highly porous scaffold plays an important role in bone tissue engineering, which becomes a promising alternative approach for bone repair since its emergence. The objective of this work was to blend poly (epsilon-caprolactone) (PCL) with chitosan (CS) for the purpose of preparation of porous scaffold. A simple unique method was employed under room-temperature condition to blend the two components together without separation of two phases. The reaction leads to formation of sponge-like porous 5, 10, 15 and 20 wt% CS composites. XRD, IR and SEM were used to determine components and morphology of the composites. DSC studies indicated that the miscibility of the two components. And pore volume fractures of composites were determined by a simple method in which a pycnometer was used. The results show that CS is successfully commingled into PCL matrix, and adding CS into PCL will not damage the crystalline structure of PCL. The composite shows no signs of phase separation and presents a unique porous structure under SEM observation. The porosity of composite increased with the increase of the content of CS in the composite. The highest porosity reached to 92% when CS content increased to 20 wt%. The mechanism of formation of this unique porous structure is also discussed.