Based on nonlinear optics and quantum theory, the process of type-II spontaneous parametric down-conversion pumped by a pulsed laser is researched in quasi-phase-matched nonlinear crystal that has a linearly chirped wave vector. The influence of the pump band-width and chirp coefficient on the properties of chirped biphotons and Hong-Ou-Mandel (HOM) quantum interference are analyzed. It is shown that with the increase of the pump band-width, indistinguishability of biphotons and quantum interference visibility are diminished while chirp coefficient is a constant; In a constant pump band-width, as the chirp coefficient is increased, the bandwidth of chirped biphotons are also increased and HOM quantum interference dip becomes narrower, thus yields enhanced the interference resolution and quantum interference visibility. Ultrabroadband biphotons and ultranarrow HOM dip are generated in theory.