Abstract: Drilling branch well can greatly improve oilfield development benefits,increase oil and gas wells productivity,and reduce damage to the environment.The key technology to drill branch wells is how to connect two well holes and make sure the mechanics integrality,waterpower integrality,and reentering ability in the joint of embranchment.’None beforehand hole’ technology is applied in Gao29-ping1 branch horizontal well.After cementing with ordinary completion methods,it is available to drill a hole as designed and then connect the main well hole and the branch well hole together based on using the special restrictive instrument.Meanwhile,the special restrictive instrument is used to realize the reentrance of the branch well.This is the first branch horizontal well completed by CNPC Jidong Oilfield as well as the first branch horizontal well designed and constructed by our country.It was put into operation on March 4,2005 with its daily output of 123.3 tons and its two branches being produced together.It is shown that the ’none beforehand hole’ technology has the advantages of simple instrument,convenient construction,reliable operation,and lower cost.