In order to study the underground oil shale insitu mining technology, FK-1 well is designed and constructed in Fuyu County of Jilin Province with completed depth of 500m, the completion layer is Nenjiang formation. The straightkeeping of large diameter drilling, open hole drilling in soft plastic formation, drilling fluid application in water sensitive formation and bit balling in mud shale formation, as well as special well completion and cementation of insitu production well are considered and overcome in the design and construction. The construction difficulties in drilling process are solved by the optimization of drilling equipments and drilling fluid performance, the corresponding optimization of well structure and the choice of drill bits and BHA. Good construction effects are received with shortened drilling time and reduced drilling investment.