The calculated distance (air line) between Zhangjiakou and Beihuaidian is approximately 177 miles respectively 285 kilometers.
By car or train, the actual journey to Beihuaidian is certainly longer, as only the direct route (as the crow flies) between Zhangjiakou and Beihuaidian has been calculated here.
Air line (approximately)
285 kilometers
154 nautical miles