Contractually, What is the correct priority of contract documents when a conflict occurs between the contractor and the owner in construction field?

This depends from the contract type, and generally the contract itself should specify the hierarchy. For example, in a LS contract, the drawings and specifications prevail over quantities (BOQs) etc etc, but of course the contract itself is the main tool for managing the obligations of the project. 

In the event of conflicts or discrepancies among the Contract Documents, interpretations will be based on the following priorities, provided, however, that the most stringent condition shall control:In the event of conflicts or discrepancies among the Contract Documents, interpretations will be based on the following priorities, provided, however, that the most stringent condition shall control:

1. The Agreement

2. Addenda, with those of later date having precedence over those of earlier date

3. The Supplementary Conditions

4. The General Conditions of the Contract for Construction

5. Drawings and Specifications

6. The Bidding Documents