I have some .xls datas in my Google Cloud Storage and want to use airflow to store it to GCP. Can I export it directly to BigQuery or can i use additional library (such a pandas and xlrd) to convert the files and store it into BigQuery? 
Thanks
Bigquery don't support xls format. The easiest way is to transform the file in CSV and to load it into big query.
However, I don't know your xls format. If it's multisheet you have to work on the file.
Import XLS file from GCS to BigQuery