The plastic deformation comes from dislocation motion in microscope. It calls for a better understanding to the mechanism in micro-structure which consists of dislocation-dislocation and dislocations-obstacles interaction. Computational model, such as discrete dislocation dynamics, has been developed, but predict the material strength at high loading rate (~1000 /s) and short time scales (~ millisecond), which is not directly comparable to most of the experiment results. A new discrete dislocation model is presented to predict plastic behavior of alloy under given temperature, loading rates and microstructure of the material. The proposed method can achieve much slower loading rates (~ 0.01 /s) and much longer time scales (~second) compared with discrete dislocation dynamics without increasing computational time. This is achieved by three innovative features: energy minimization to model dislocation glide and eliminate associated time scale; thermal activation over obstacle to accommodate variety of strengthening mechanism; fully couple mechanics-diffusion framework to capture dislocation climb. The numerical result shows the rate effects and thermal effects of an obstacle-strengthened material. It also demonstrates high temperature creep for nickel based super alloys.