Stress-strain behavior, orientation and crystallinity were measured for the LDPE blown films filled with CaCO, tc, establish relationship between mechanical properties and processing condition with different filler content. It has been found that, under the constant extrusion temperature and cooling condition, the mechanical properties of CaCO₃-LDPE polymeric composite blown films were depended on the processing condition, and that MD and TD mechanical properties were balanced at blow-up ratio of 2, and draw-down ratio of about 8. The Young''s modulus of films was increased but tensile strength and elongation decreased with increasing CaCO₃ content. At constant blow-up ratio. j~he increase in draw-down ratio increases the MD molecular orientation and decreases the TD molecular orientation, thu3 we conclude that molecular chains were taken preferential orientation to MD. But for the constant draw-down ratio, the incaease in blow-up ratio increases the TD molecular orientation. For the composite films the MD and TD molecular orientation were decreased with increasing filler content At constant blow-up ratio of 2. the degree of crystallinity of films was slightly increased with increasing draw-down ratio and filler content.