We have studied symmetric cosmic ray intensity decreases (V Shape, and U Shape) magnitude 2.0 , observed at Oulu super neutron monitor, during the period of 1986-2006 with coronal mass ejections CMEs), interplanetary shocks and disturbances in solar wind plasma parameters (solar wind temperature, velocity, density). We have found that 76.92% V shape symmetric cosmic ray intensity decreases are associated with halo and partial halo coronal mass ejections (CMEs). The association rate between halo

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... and partial halo coronal mass ejections are found 40.00%and 60.00% respectively. Most of the V Shape symmetric cosmic ray intensity decreases are related to interplanetary shocks (61.53%) and the related shocks are forward shocks. We have also found positive corelation with co-relation co-efficient 0.54 between magnitude of V shape symmetric cosmic ray intensity decreases and speed of associated coronal mass ejections. From the further study it is concluded that V shape symmetric cosmic ray decreases are strongly related to the disturbances in solar wind plasma parameters. Negative co-relation has been found between magnitudes of V Shape symmetric cosmic ray intensity decreases and magnitude of jump in solar wind plasma density of associated JSWD events with corelation co-efficient -0.152 between these two events. Negative co-relation has also been found between magnitude of V Shape asymmetric cosmic ray intensity decreases and magnitude of jump in solar wind plasma velocity of the associated JSWV events with corelation co-efficient -0.48 between these two events. From the study of U Shape symmetric cosmic ray intensity decreases and disturbances in solar wind plasma parameters, we found negative co-relation with correlation coefficient, -0.473 between magnitude of U shape symmetric cosmic ray intensity decreases and magnitude of jump in solar wind plasma temperature of associated JSWT events, -0.468 between magnitude of U shape symmetric cosmic ray intensity decreases and magnitude of jump in solar wind plasma density of associated JSWD events and -0.26 between U shape symmetric cosmic ray intensity decreases and magnitude of jump in solar wind plasma velocity of associated JSWV events.