We used two experimental results with different fidelity to build surrogates which is employed to estimate the contours of a complex function. Our goal is to improve efficiency by using the same or less computational budgets. We propose a criterion to decide which level of the code to perform at added points for sequentially refining the estimated contour. Some discrepancy measures are used to assess the quality of estimated contours. The proposed method is used to estimate the average delay time in a queuing network system.