This paper elaborates concisely the methods of stochactic analysis in finance and insurance. By the stochastic analysis for some acts about finance and insurance, the paper extends the question of option pricing and explains profoundly the method of risk neutral probability (equivalent probability measure) . Moreover, a pithy and elegant testimony together with the testimony by the way of martingale is provided by discussing ruin probability in risk models in the paper, which discusses the method of martingale pricing about mortgage insurance in Hull—White model at last. |