For scan-based testing, the high test power consumption may cause test power management problems, and the extra scan chain connections may cause routability degradation during the physical design stage. In this paper, a scan chain ordering technique for test power reduction under user-specified routability constraints is presented. The proposed technique allows the user to explicitly set the routing constraints and the achievable power reduction is rather insensitive to the routing constraints. The proposed method is applied to six industrial designs. The achievable power reduction is in the range of 37-48% without violating any user-specified routing constraint.