Abstract: When steerable assembly with two stabilizers and one bend was used to drill a section in composite drilling mode,the well trajectory would always deviate from the designed well trajectory.To solve this problem,the angle holding-inclination capability of steerable assembly with two stabilizers and one bend,as well as factors affecting it were analyzed.Based on the quasi-dynamic model for side force of steerable assembly,a computer program was developed to simulate the effects of structural parameters,inclination and weight on bit(WOB)on holding-inclination performance of steerable assembly with two stabilizers and one bend.The results show that if the O.D.of the first stabilizer is too small,the stabilizer will have no contact with borehole.And as the increase of O.D.of the second stabilizer,the rotary side force of steerable assembly with two stabilizers and one bend decreases.In addition,the effects of the bent angle of PDM,inclination,and WOB on the rotary side force of steerable assembly with two stabilizers and one bend are all slight.By using the above simulated results,steerable assembly with two stabilizers and one bend was designed to hold-inclination in Well NP13-X1025.The result of actual drilling indicates the optimized assembly works well in holding-inclination,with the inclination curvature being only 0.18°/30m.It is concluded that,the holding-inclination capability of steerable assembly with two stabilizers and one bend can be improved by optimum design according to the analysis of its influencing factors.