Abstract: According to practical drilling on site,in laboratory the average recovery rate of core permeability can be up to 89% and its recovery rate is improved to 93% after nitrogen penetrates adversely the core damaged statically and dynamically by ASS-1 drilling fluid system.The pressure less than 1.0MPa at which the mud cake lifts off shows that the temporary plugging is cleaned up easily by pressure on oil formation or gas formation without other methods.It also demonstrates that the size of temporary plugging particle conforms with the size of capillary in formation and soft material content with plugging agent or chemical in formation makes the damage to formation of ASS-1 system very light.After the section of the core long about 1cm is cut off from damaged end,the permeability increases sharply,up to average 137% and which shows that the depth of damage is less 1cm.At last,it is found that there is no immerging particle in the lacuna of core and ASS-1 drilling fluid system only plugs the lacuna at the surface of cores by scan electronic microscope (SEM).The studies above suggests that the choice of carbonate calcium as temporary plugging Particle is reasonable and effective and the plugging on formation happens only on the wall of well to protect formation from damage in the course of drilling and the using area of drilling and the using area of ASS-1 drilling fluid system can be extended to the field of drilling.