This article is interested in SMT with NRA theory. This theory is associated to a solver based on Interval Constraint Propagation (ICP) techniques which is easily implementable with IBEX library. The contribution of the paper is the definition of an algorithm dedicated to the conflict analysis step. This algorithm is an adaptation of the QuickXplain algorithm, mainly dedicated to discrete domain Con- straint Satisfaction Problems (CSP), to continuous or numerical CSP.