A novel controllable cold neutral atom guiding scheme based on parallel current-carrying wires and bias magnetic field is proposed. Magnetic field distribution in cross-section at different transverse bias field Bbx is calculated. The centre of magnetic traps is discussed. Single-channel and double-channel magnetic guiding can be realized. Based on this scheme, an atom beam splitter, which has adjustable splitting ratio, is designed by adding a longitudinal magnetic bias field Bby. The transverse distribution of magnetic trap is calculated, and the magnetic contour plane of the splitter is shown. By using the classical Monte-Carlo method, the splitting process is simulated, and this scheme is validated by the simulation results. Splitting ratio between left and right guide changes from 0.9/0.1 to 0.1/0.9 when longitudinal magnetic bias field Bby changes from -0.005 G to 0.005 G.