Abstract: The relationship between the variations of galactic cosmic ray intensity and geomagnetic storms from 1966 to 1983 is studied in this paper. The variations of the cosmic ray intensity during a sudden commencement pulse Si doesn't show an obvious decrease. Avery small Forbush decrease appears during gradual commencement storm G_c. On the other hand, there is a very obvious Forbush decrease during sudden commencement storm S_c. Then S_c storms are classified into S_A, S_B, S_D. S_d and S_b storms on the basis of Kindex. The results of analysis show that Forbush decrease of cosmic ray intensity during S_A storms is the most obvious and the decreasing rate and recovering rate are also the fastest. The amplitutes of Forbush decrease are descending in the order of S_A, S_B S_Dand S_d storms. Their decreasing rates and recovering rates become slowing in the same order. But the cosmic ray intensity during S_b storms has no obvious decrease. According to corresponding relationship between Kcategory of magnetic disturbances and. interplanetary disturbances, a relation between cosmic ray intensity variations and interplanetary disturbances is obtained.