This thesis studied volatility models for option pricing and their calibration methods using the optimal transport theory. The author first introduced theoretical results by casting a class of volatility model calibration problems as a type of convex optimisation problem. Based on the established results, the author proposed calibration methods with numerical methods to calibrate the local volatility model, stochastic volatility model and a joint model for SPX and VIX. The proposed methods efficiently and accurately capture the market dynamics.