The present disclosure belongs to the field of petroleum exploration and development and, in particular, relates to a system and a method for analyzing while-drilling rock fragments in oil and gas field. The system includes a sample preparation mold and a sample scanning apparatus; the mold is configured to quickly batch prepare fragments into scanning ready samples; the apparatus is portable and configured for batch scanning and analyzing the samples, and having the capabilities of anti-vibration, temperature control, dust prevention, and adaptability to a harsh well site environment; the method includes a scanning step where surface images, elements and mineral types of rock can be rapidly quantitatively analyzed, and lithologies thereof can be identified; the method also includes the analysis step in which rock's elastic parameters and target zone of the vertical well are determined, and geosteering and design of staged fracturing of horizontal well can be provided.