By means of the BCS wave functions and projected wave functions the absolute values of a reduced width of even-even isotopes of 84Po and odd-even isotopes of 85At are calculated. The change of absolute values and the behaviour of the relative values due to the change of the parameters b, R0, and G have been investigated, where b is the parameter of harmonic oscillator well, R0 the channel radius, and G the parameter of pair correlation. The analysis of the results of calculation shows that:(1) Pair correlation favours the formation of a particle; it may increase the reduced width by an order of magnitude, and it may induce the relative behaviour to be more compatible with experiment.(2) The nonconservation of particle number of BCS wave function is a serious defect for those nuclei for which the number of particles outside the closed shell is few. The projected wave function, for which the number of particles is conserved, may increase the absolute values by 1-2 times, and may improve the relative behaviour.(3) On taking account of the blocking effect, the reduced width may decrease by 10%, this has the result that the hindered factors of odd A nuclei may agree with the experimental values.(4) The absolute values are very sensitive to the selection of parameters, but the relative behaviour is not very sensitive. In order that the absolute values may approach the experimental values, R0 should be within 8f.