Abstract: Topological insulators are a class of quantum materials which have unique surface states that follow Dirac energy dispersion and are topologically protected by time-reversal symmetry. The recently discovered topological crystalline insulators (TCIs), a SnTe material class, expand the ever-growing family of topological insulators. Instead of time-reversal symmetry, crystalline symmetry protects the topological phase in TCIs. By doping SnTe, we study topological properties of SnTe. First, we dope SnTe with Indium, a candidate of a topological superconductor. In-doped SnTe can provide a platform to create Majorana fermions and realize topological quantum computing. Second, Selenium is doped into SnTe to effectively reduce the bulk carrier density, a critical step toward the use of the surface states.