how to fix position of wordpress admin pointer(tour)

Solution:

By default wp-pointer.js will set pointer position to absolute except the case where the target has position fixed. Using show event you can change pointer CSS:

<script type="text/javascript">
jQuery(document).ready(function($) {
    $('li#toplevel_page_mymenu_admin_page').pointer({
        content: 'test_message',
        position: {
            edge: 'top',
            align: 'center',
        },
        show: function(event, t){
            t.pointer.css({'position':'fixed'});
        },
        close: function() {

        }
    }).pointer('open');
});
</script>