Steerable drilling technology has been successfully applied in Shengli Oilfield. Hundred millions RMB cost was saved from 300 wells. Steerable drilling technology made notable technical-economic benefit during drilling inclined section and horizontal section. During theoretic research and field practice, we researched the steerable drilling horizontal section, programmed the mechanical analysis software of steerable drilling assembly with Weighted Residuals Method, and studied the rotary drilling build-angle force. Finally, some valuable conclusions are obtained from theoretic research and field practice, and the paper presented some proposals on further improving the horizontal drilling ability of single-benthousing, single-stabilizer type steerable drilling assembly.