The observational data (e.g., the timing data and magnetic tilt angles χ) of young pulsars can be used to probe some critical issues about the internal physics of neutron stars (NSs), for instance, the number of precession cycles ξ and the internal magnetic field configuration (IMFC) of NSs. Evolution of the dipole magnetic field Bd of NSs may play an important role in determining the final results. In this work, a power-law form is adopted to describe the decay of Bd. In such a scenario, the IMFC and ξ of young pulsars with an ordinary Bd∼1012−1013 G and a steady braking index n are investigated. Since the tilt angle change rates χ˙ of pulsars with n<3 can be theoretically predicted, a test on the power-law decay model can thus be made by comparing the theoretical values to that obtained from observations. However, such a comparison can only be made on the Crab pulsar currently, and the results show that the power-law decay model is inconsistent with the Crab's observations. We suggest that rather than decay, the Crab's Bd should increase with time at a rate ∼12−14 G/s. A definite conclusion on the validity of the power-law decay model for pulsars with ordinary Bd may be given if χ˙ of other pulsars could be measured.