how to get access subview of UIView?

You can use view’s tag property:

UIImageView *imageView1 = [[[UIImageView alloc] init] autorelease];
imageView1.tag = 100;
UIImageView *imageView2 = [[[UIImageView alloc] init] autorelease];
imageView2.tag = 200;
imageView2.alpha = 0;
[cell.accessoryView addSubview:imageView1];
[cell.accessoryView addSubview:imageView2];

And later get subview using -viewWithTag: method:

UIImageView *getImageView1 = (UIImageView*)[cell.accessoryView viewWithTag:100];