A 3D quantum time-dependent wave packet method using reactant Jacobi coordinate for calculating reactive resonance wave functions was applied to investigate the $$\hbox {F}+{\hbox {H}}_2/\hbox {HD} \rightarrow \hbox {HF} + \hbox {H}/\hbox {D}$$ reactive resonances. By transforming the scattering resonance wave function into product Jacobi coordinates and calculating the 1D rovibrational resonance potential curves using the adiabatic bender model, the nature of the resonances was clearly deciphered. It was found that the resonances without rotational excitations enhance the reactivity; however, the resonances with rotational excitations depress the reactivity significantly. The difficulty for time-dependent method for efficiently describing the $$\hbox {F}+{\hbox {H}}_2/\hbox {HD}$$ at energies around reactive resonances is explained. The collision-energy-dependent differential cross sections around the dynamical resonance states are presented for revealing the effects of reactive resonances to the observables in a molecular crossed-beams experiment.