Abstract: Based on the large-scale configuration of the magnetic fields in the interplanetary space and the possible association of the solar wind flow near the sector boundary crossing with the coronal streamer,it is suggested that in the interplanetary space there might be some spiral sector transition regions which are thicker than the sector boundaries.In situ observations of interplanetary magnetic field and solar wind plasma do show the existence of the spiral sector transition regions.The magnetic strength in the regions does not go to zero for all the 45 cases studied in this work,most of them have the magnetic strength either much higher or much lower than the average of 5γ in the adjecent magnetic sectors.The physical properties in the magnetic depressing (MD) and magnetic enhancement (MB) regions and the possible rauses have also been analyzed and discussed.