Abstract: In terms of certain conditions, to use the assembly of bevel strings is one of the best effective fleet inclinedproof drilling techniques. The forcereceived estate of assembly of bevel strings which is applied in the technique of bevel strings fleet inclinedproof is very complex and greatly affects the security of whole drill string system. In order to realize a safe, effective drilling operation, to analyze the strength of bevel joint and its neighboring drill collars is very necessary. At the same time, it′s very important to find out the danger point of assembly, and it′s very expediently to proofread the strength of drilling strings and improve its structural design. Some research indicates that the most compound stress of bevel inclinedproof strings is commonly situated in the bonding site of bevel joint and underneath drill collar which is derived from the bend load and axial force. In the most dangerous place, the security of drilling tool′s strength should be concerned especially.

Key words: BHA with eccentric sub, deflection controlling &, drilling fleetly, strength, finite element analysis, high dip structure