[en] Ba_0.67K_0.33BiO_3+δ single crystal with T _c ∼ 26.4 K has been prepared by the molten salt electrochemical method. We observed a four-fold symmetry in the angular dependence of ab-plane resistance R (θ) at H = 0.5 T and T = 25.5 K for the first time. The data can be scaled by R = [R ₁sin²(θ + 45°) + R ₂cos²(θ + 45°) − R(90°)]|sin2θ| + R(90°). Although dip structure appears in R(θ) when the angles between the magnetic field direction and c-axis are 0°, 90°, 180° and 270°, respectively, the maximal position of resistance tilted away θ = 45° and θ = 135°, namely the angle difference between two peaks is 79° or 101°. This result indicates the superconducting Ba_0.67K_0.33BiO_3+δ single crystal is probably an orthorhombic structure with distorted Bi−O octahedron. We consider that the angular dependence of resistivity comes from the superconducting energy gap with ${d_x}^2{{}_{-<!--\; ???\; -->y}}^2$ pairing symmetry. The flux pinning energy for θ = 90° is higher than that for θ = 135° proves the existence of the anisotropic vortex pinning effect. The field dependence of flux pinning energy displays a power law, U ∝ H ^−α. The irreversibility line was also discussed. (paper)