By using a microsecond pulse field, we succeeded in fabricating a uniform submic ron domain pattern with a period of 1.7μm in LiNbO3- doped 5mol% MgO. And the depth of these domain strips is, typically, about 30 to 50μm. When a pol ed field with a pulse width of 100ms is applied, the domain- inverted structure with a width of 0.5μm was obtained. Using the spontaneous domains backswitc hing and domain side- grown effects, we can explain the mechanism of the submicro n domains evolution.