This work focuses on the numerical approximations of random periodic
solutions of stochastic differential equations (SDEs). Under non-globally
Lipschitz conditions, we prove the existence and uniqueness of random periodic
solutions for the considered equations and its numerical approximations
generated by the stochastic theta (ST) methods with theta within (1/2,1]. It is
shown that the random periodic solution of each ST method converges strongly in
the mean square sense to that of SDEs for all step size. More precisely, the
mean square convergence order is 1/2 for SDEs with multiplicative noise and 1
for SDEs with additive noise. Numerical results are finally reported to confirm
these theoretical findings