289 Forbush Decrease effects (FD) were processed, for 207 of which corresponding flares were determined. The following parameters of FDs were determined from cosmic ray recordings at the Alert station: start of FD, time of first or second minimum value, the time lag of the beginning of FD behind the source flare, the
duration of the descending phase, the decrease of FD in per cent, the duration of the whole decrease effect and the rate of decline phase. The occurrence of FDs in the years of solar cycle No. 21 and the distribution of source flares over the solar disc was demonstrated (including NS oř EW asymmetry). In the II part will be
published the statistical distribution of the individual parameters of FDs and their mutual relations. The values of the FD parameters are also related to the importance and also to the longitudinal position of the flares. Some results of studied relations were used for interpretations of the characteristics and shape of the magnetic plasma cloud.