Hide category from the Home Query

functions.php

// More info: http://codex.wordpress.org/Plugin_API/Action_Reference/pre_get_posts
function hide_cat_home_query ( $query ) {
	if ( $query->is_home() && $query->is_main_query() ) {
		$the_cat_id = get_cat_ID('cat_name');
		$query->set('cat', '-'.$the_cat_id);
	}
}
add_action('pre_get_posts', 'hide_cat_home_query');