A bearing assembling method is proposed based on analysis calculation of bearing assembling method, pre-tightening amount, pre-tightening load, lubrication and sealing. The shafting structure precision of the precise opto-electronic turntable is discussed. The unique shafting assembling method is used in prototype assembling, and the bearing pre-tightening amount is converted into the regulation of the end-cover thickness. Not only the pre-tightening problem during shafting assembling is resolved but also the shafting precision is guaranteed. Assembling and debugging experiments show that the assembling method can guarantee the best pre-tightening effect and provides basis for the turntable stable running and high precision tracking, which has better actual guidance.