Hello srikant,

Below is the code updated to be bulkified. Although I have had some difficulty uinderstanding some of your code. Specially this part:

Points__c[] fn =[select id,account__c,opportunity__c from Points__c where opportunity__c=:o.id];

and then here:

if(fn.size()>0{

fn[0].Points_Transaction_Amount__c=o.amount-o.amount*2;

 Basically you are getting a list of points for a given Opportunity, BUT then you only look at the first returned points record for the Opportunity and update only that one. Is this on purpose or do you actually want to update all the points for the Opportunity??

Anyhow, below is the bulkified code, I do hope it helps you.

trigger pointamount on Opportunity ( after insert,after update,before delete){
//add this list to hold points__c records to insert all at once.
List<points_c> points;
List<points__c> pointsDEL;

 if(trigger.isInsert)  {
	for (Opportunity  o : Trigger.new){ 
		if(o.accountid!=null && o.Purchase_Type__c == 'Pilot'&& o.Catalog_Source__c== 'SimCenter'){
			points__c  a = new Points__c();
			a.Account__c = o.Accountid;          
			a.Points_Transaction_Amount__c =o.amount-o.amount*2;
			a.Points_Transaction_Reason__c =' Points Redeemed';  
			a.Points_Transaction_Date__c=o.CloseDate;
			a.Purchaser_Email__c=o.Contact_Email__c;
			a.Opportunity__c=o.id;
			a.Purchaser_Name__c=o.Purchaser_Name__c;
			points.add(a);
		}
	}
	Database.insert(points);
	points = null;
	//If you would prefer to insert the records and not have the DML transaction fail if one of the records insert fails then use this: Database.Insert(points,false); 
 }
 
 
  if(trigger.isupdate) {
  //WHY ARE YOU USING fn[0] to get the points?? This would only get the first record in the array, not any other if there are more than one.
	for (Opportunity  o : Trigger.new){
		if(o.accountid!=null && o.Purchase_Type__c == 'Pilot' && o.Catalog_Source__c == 'SimCenter'){
			Points__c[] fn =[select id,account__c,opportunity__c from Points__c where opportunity__c = :o.id];		
			
			if(fn.size()==0){
				points__c  a = new Points__c();
				a.Account__c = o.Accountid;          
				a.Points_Transaction_Amount__c =o.amount-o.amount*2;
				a.Points_Transaction_Reason__c =' Points Redeemed';  
				a.Points_Transaction_Date__c=o.CloseDate;
				a.Purchaser_Email__c=o.Contact_Email__c;
				a.Opportunity__c=o.id;
				a.Purchaser_Name__c=o.Purchaser_Name__c;
				points.add(a);
			}
			if(fn.size()>0){
				//I dont understand why you only look at the first record here( fn[0] ), do you not want to update ALL points records for the Opportunity??? 	
				fn[0].Points_Transaction_Amount__c = o.amount-o.amount * 2;
				points.add(a);
			} 
		}
	}
	//IF there are new points to insert for the Opportunities they will be inserted into database, if there are existing ones they will be updated
	if(points.size()> 1) Database.Upsert(points);
	
}

if(trigger.isdelete  ){
	for (Opportunity  o : Trigger.old){
		if(o.accountid!=null &&o.Purchase_Type__c == 'Pilot'&& o.Catalog_Source__c== 'SimCenter'){
			Points__c fn =[select id,account__c,opportunity__c from Points__c where opportunity__c=:o.id  ];
			pointsDEL.add(fn);
		}
	}
	Database.delete(pointsDEL);
}

}