Liquid crystalline blue phases (BPs) have very unique characteristics. However, the mechanism of appearance of BPs has not been understood completely. On the other hand, elastic distortions of liquid crystal can be classified into terms based on elastic constants: K1 (splay); K2 (twist); and K3 (bend). The elastic constants can provide with important information about intermolecular interaction in liquid crystals, BPs are expected to be unstable in the case of large K3. The elastic ratio (K3/K1) of liquid crystal mixture can be changed by mixing ratio of strong and weak polar liquid crystals. In this study we investigate influence of elastic constants upon appearance of BPs.