Plastic deformation and dislocation accumulation in dispersion hardening alloys are numerically analyzed by a crystal plasticity finite element technique and work hardening characteristics are discussed. The critical resolved shear stress for slip system is given by the extended expression of the Bailey-Hirsch type model which include the Orowan stress as size effect of microstructure. Work hardening of slip system is estimated by statistically stored dislocation (SSD) density. Increment of the SSD density is evaluated by slip strain and the mean free path of dislocations (the Kocks-Mecking model). The mean free path depends on the average spacing of dispersed particles, which is also used to estimate the Orowan stress. The average spacing of dispersed particles is calculated from the volume fraction and average diameter of dispersed particles. As a result, flow stress level at the initial stage of deformation agreed very well with experimental result but work hardening rate was higher than that of experiment. From this fact, it is considered that the mean free path and the average spacing of dispersed particles are different spacing factors. When we assume that the mean free path is two to three times larger than the average spacing of dispersed particles, numerical result of the strain hardening agrees very well with experimental one.