The invention discloses a large-curvature radioactive level horizontal drilling process and device includes drilling vertical well to oil layer, lowering the sleeve, drilling sleeve shoe, building up angle directionally, washing well, lifting the drill, lowering special sieve vessels, filling with gravels, decoupling the hanger for circulated well washing, lifting the hanger de-coupler and all drilling tools above, drilling other radial wells, etc. Through drilling a plurality of radial wells, the invention enlarges seepage area, expanding seepage range, increasing the daily production for single well and raises final recovery ratio, so as to achieve the purposes of making full use of energy, increasing economic benefits and benefiting the society.