The traditional Ag sheath has both good chemical compatibility and plastic processing characteristic with iron-based superconductors (IBS), but it possesses too low mechanical strength. Employing composite sheathes is a direct, efficient and low-cost method to prepare high strength Ba1-xKxFe2As2 conductors. In this paper, the Ba1-xKxFe2As2 multifilamentary wires/tapes with stable structure and large ductility were obtained through optimizing the sheath size, cold deformation and intermediate annealing. It is found that the shape distribution of multi-cores is uniform, and the superconducting filling factor is about 25.3-28.0% for our Ag/Nb/Cu composite sheathed Ba1-xKxFe2As2 superconductors. The magnetic critical transition temperature Tc of Ba1-xKxFe2As2 tape is up to 37.5 K, meanwhile the magnetization of hysteresis loops (M-H) shows a strong flux pinning ability. The transport critical current density Jc of Ba1-xKxFe2As2 tape is about 1.0×104 A/cm2 at 4.2 K and 2 T, and still holds 8.7×103 A/cm2 at 10 T.