A 3,4-dihydroquinazoline derivative or a pharmaceutically acceptable salt thereof and a composition containing the same are provided. The 3,4-dihydroquinazoline derivative or a pharmaceutically acceptable salt thereof show activities of blocking an intracellular influx of calcium ions acting as a secondary signal essential to the proliferation and growth of cancer cells, thereby inducing the cell cycle arrest of cancer cells, and eventually reinforcing the efficacy of existing anti-cancer drugs. A combination comprising the above compound and another anti-cancer drug is also provided.