The impact strength and the flexural modulus are important properties for industrial use of polymer materials. However, because these two properties are usually considered as trade-off, enhancing one of the properties causes decreasing the other. The impact strength not only at ambient but also at low temperature is required for practical use. In general, the impact strength drastically decreases at low temperature. Here, we introduce a method for enhancing impact strength at room and low temperature without reduction of flexural modulus. Polycarbonate (PC)/low density polyethylene (LDPE) polymer alloys of 0.6, 1 and 10% in weight ratio of LDPE were prepared by melt compound. The impact strength is controlable by LDPE addition, and the values of PC and the alloys at 23oC and -45oC are 65.0 and 8.7 kJ/m2 (PC), 81.3 and 8.9 kJ/m2 (0.6 wt%), 78.3 and 12.3 kJ/m2 (1 wt%), 60.1 and 43.2 kJ/m2 (10 wt%). The impact strength of PC with 1% of LDPE alloy at room and low temperature are 20% and 40% higher than those of PC, respectively. The flexural modulus of PC/LDPE 1 wt% alloy is 2.4 Gpa, and the value is almost same as that of PC (2.2 GPa). The impact strength at room and low temperature are enhanced without reduction of the flexural modulus. Morphologies of PC/LDPE alloys show sea-island structure and gaps are formed at the interfaces of PC matrix and LDPE particles. In other words, cells were formed by non-contact interfaces of PC and LDPE. The cells and the particles diameters increase with increasing LDPE content. We will report the relation between the morphologies and impact strength in the presentation.