The invention discloses an optimization design method for a step stress accelerated 
degradation test based on a Bayesian theory, and is applied to the technical field of the accelerated 
degradation test. The optimization design method comprises the steps as follows: firstly, determining product performance degradation and acceleration models, and based on the historical data, giving prior distribution of 
model parameters; secondly, determining an optimization 
design space, and forming a test scheme set; thirdly, creating an expected utility function or an expected 
loss function, determining optimization goals, and based on a 
Markov Chain Monte Carlo method, determining optimization goal values of designs in the test scheme set; and lastly, finding the 
optimal test scheme by using a 
curve fitting method. According to the optimization design method, the shortcoming of high possibility of larger deviation due to the implementation of the traditional (local) 
test optimization design method when the values of the 
model parameters are supposed to be known is avoided, and the optimization scheme obtained in the implementation of the 
test optimization design when the prior distribution of the 
model parameters is given is more reasonable and more actual.