Abstract: The working mechanism,laboratory test and field using of a novel water glass blocking agent is described,and it is made of water glass using single fluid method.In contrary to the conventional blocking agent,which has poor strength,low blocking rate and poor temperature tolerance,the new blocking agent has many advantages.It has long initial and terminal setting time,which ensures the safety operation with tools in the hole.by adding a certain kind of additive,the blocking agent can form even blocking without onrushing,and it has higher strength and good acid resistance,this eliminates the use of packer for formation protection during plugging resolving operation.Further more,it has high temperature tolerance,long valid period and low viscosity,thus it is suitable for sealing the water zones and can also be used for selective water blocking to bottom water production zones by controlling pumping rate.As compared with other water blocking agents,it needs lower operation pressure,which is good for water blocking in the depleted wells with casing of low strength and in the wells with thin-bedded reservoirs.In addition,forwells of extrusive inter-formation inconsistencies,the higher acid resistance of the blocking agent makes it possible to conduct water blocking operation to the high permeable formations and acidizing operation to the low permeable formations,thus realizes the aim of adjusting water injection profiles.