I found this useful from the woocommerce developer documentation. 

You can simply call is_woocommerce_active() function within your plugin file.

Example
``
if ( ! is_woocommerce_active() ) 
{
	add_action( 'admin_notices', 'WC_Subscriptions::woocommerce_inactive_notice' );
	return;
}
``

**is_woocommerce_active** defined as below as per woo documentation
``
/**
 * Check if WooCommerce is activated
 */
if ( ! function_exists( 'is_woocommerce_activated' ) ) {
	function is_woocommerce_activated() {
		if ( class_exists( 'woocommerce' ) ) { return true; } else { return false; }
	}
}
``