Thank you all !
My algorithm is an improvement of LPA*, thus, it needs a heuristic estimation like the one of A*.
As Michael said, I look at the coordinate system of my shapefiles, and found out that it is in "GCS_Assumed_Geographic_1". So, i change the Geographic Coordinate System to Projected Coordinate System using Project tool in ArcToolbox. (i changed it to NAD_1983_California_Teale_Albers, pretty uncertain about how they work :D). Is that OK?
After that, i re-create my network dataset and check out the distance using Pythagorean theorem. It work ! The result is real distance in meter 😄