I have followed the below steps from wiki page as mentioned  Sam and Ralph. Now my requirement is working fine. Thanks Sam and Ralph for the valuable information.

Automatically set the value of an attribute based on state

Solution: Use a calculated value customization

1. Note: The presented solution is experimental and should be used with caution:
   • This technique may not work with all attribute types.
   • The behavior of the Eclipse UI and the Web UI differs.
     • When using Eclipse, the value of an attribute is updated as soon as an item is saved.
     • In the Web UI, the value of an attribute stored on the server is updated as soon as an item is saved. However the value visible on screen is not updated in that case. If you need to see the new value you should refresh the web page. Note that the data on the server contains the correct value and this is just a UI issue.
   • It is recommended to combine this method with Owner must be a predefined user to assure data integrity.
2. Create a new script-based calculated value provider. In the following we set the Owned By attribute of an item to a specific user when the item is in a particular state.

   dojo.provide("org.example.CalculatedOwner");
   
   dojo.require("com.ibm.team.workitem.api.common.WorkItemAttributes");
   
   (function() {
   var WorkItemAttributes= com.ibm.team.workitem.api.common.WorkItemAttributes;
   
   var CalculatedOwner= dojo.declare("org.example.CalculatedOwner", null, {
   
       getValue: function(attributeId, workItem, configuration) {
           if (workItem.getValue(WorkItemAttributes.TYPE) === "defect" && workItem.getValue(WorkItemAttributes.STATE) === "4") {
               return configuration.getChild("parameters").getStringDefault("owner", "");
           } else {
               return workItem.getValue(WorkItemAttributes.OWNER);
           }
       }
   });
   })();
   		

   Note that you must always return a value that will be assigned to the Owned By field. In case the item is in the Verified state (index 4) we use a value that is configured in the project specification. Otherwise we use the current value of the Owned By field.
3. This script requires a configuration entry in the process specification:

   <valueProvider id="calculatedowner" name="Calculated owner" providerId="com.ibm.team.workitem.shared.common.internal.valueProviders.ScriptAttributeValueProvider">
       <script class="org.example.CalculatedOwner" path="/workitem/scripts/common/CalculatedOwner.js"/>
       <parameters owner="_r4ct4I2vEeCCZ-jvhw8VFA" />
   </valueProvider>
   		

   The owner attribute defines which user needs to be set as owner. To get the user id for a particular user see Get an item's UUID.
4. Finally assign this customization to the Owned By attribute in Work Items > Types and Attributes. Make sure to add dependencies on the Type and Status attributes since these are required for the calculation to work properly.
5. This customization will allow any user to be selected as the owner of a defect as long as the defect is not in the Verified state. Once the defect is put into the Verified state the system will automatically set the owner of the item to the predefined user in the process specification.