The biaxial crystal dynamic outer conical refraction is obtaieded.After using kNbO3 and the solid-state laser emitted green beam,the transmission aperture of iris located in the back surface of aplanatic cemented double lens,is alternated in order to carry out that the incident light convergent angle modulate the outer conic refraction angle,so that the angle expression about outer conic refraction of biaxial crystal kNbO3 is accomplished.The experiment shows that the outer conical refraction angle synchronously varies when the size of iris aperture is alternated in periods and the angle is equal to the convergence angle of the beams,which incident to the end face of the biaxial crystal.The biaxial crystal dynamic outer conic refraction can be applied in the fields of laser radar and photric scanning.The theory calculation is coincident with the tested data.