Abstract: The coronal mass ejections （CMEs） are the most important source causing calamitous space weather. If a CME carries strong southward magnetic field component and last for a prolonged period of time then it can cause geomagnetic storm with sudden commencement, otherwise it just causes geomagnetic sudden commencement. Both geomagnetic activities have sudden commencement. The paper analyzes the geomagnetic sudden commencement number （GSCN） series with wavelet technique to get its periodic properties and the results show that the most evident periods of the GSCN are the periods around 11 years, the strongest period of the GSCN is 10.556 years and reaches its maximum in the year 1948. Two weaker periods of the GSCN are the periods during 16-32 intervals and the periods during 32-64 intervals. The strongest period for the interval 16-32 years is 24.25 years, while the strongest period for the interval 32-64 years is 42.22 years. The paper also computes the correlation coefficient between sunspot number series and geomagnetic sudden commencement number series, the correlation coefficient of the two series is 0.8896. The correlation coefficient of the sunspot number series and geomagnetic storm with sudden commencement number series is 0.8492 which is lower than 0.8896. Though the correlation coefficient of the sunspot number data series and geomagnetic sudden commencement is high, the periodic properties of the two series are not the same. Firstly the periods of the GSCN around 11-year are not the same for the two series, secondly the periods between 16-32 years of the GSCN are more evident than that of sunspot number series, thirdly the periods between 16-32 years of the sudden commencement series are still more evident than that of sunspot number series.