Web crawler should maintain fresh data with minimum server overhead for large amount of data in the web sites. The overhead in the server increases rapidly as the amount of data is exploding as in the big data era. The amount of web information is increasing rapidly with advanced wireless networks and emergence of diverse smart devices. Furthermore, the information is continuously being produced and updated in anywhere and anytime by means of easy web platforms, and smart devices. Now, it is becoming a hot issue how frequently updated web data has to be refreshed in data collection and integration. In this paper, we propose dynamic web-data crawling methods, which include sensitive checking of web site changes, and dynamic retrieving of web pages from target web sites based on historical update patterns. Furthermore, we implemented a Java-based web crawling application and compared efficiency between conventional static approaches and our dynamic one. Our experiment results showed 46.2% overhead benefits with more fresh data compared to the static crawling methods.