Power control is a mandatory method in CDMA based system, including in high altitude platform station (HAPS) WCDMA system evaluated in this paper. HAPS is a new means of wireless delivery method located at stratospheric layer and act as the base station providing the communication systems. Platform located at that layer will be affected by the wind. Therefore, the platform is supposed to move from original position and then experience an instability condition. In this paper, this practical situation of HAPS will be evaluated in term of the power control performance. We evaluate two distance-based power control schemes for the downlink HAPS channel. The first scheme is an optimum power control and the second scheme is n^th power of distance power control. Computer simulation shows that the performance of distance-based power control scheme is significantly affected by the movement of HAPS.