A novel general formula for on-axis sun-tracking system has been introduced and derived to allow the sun tracker to track the sun in two orthogonal driving axes with any arbitrary orientation (Chong & Wong, 2009). Chen et al. (2006) was the pioneer group to derive a general sun-tracking formula for heliostats with arbitrarily oriented axes. The newly derived general formula by Chen et al. (2006) is limited to the case of off-axis sun tracker (heliostat) where the target is fixed on the earth surface and hence a heliostat normal vector must always bisect the angle between a sun vector and a target vector. As a complimentary to Chen’s work, Chong and Wong (2009) derive the general formula for the case of on-axis sun tracker where the target is fixed along the optical axis of the reflector and therefore the reflector normal vector must be always parallel with the sun vector. With this complete mathematical solution, the use of azimuth-elevation and tilt-roll tracking formulas are the special case of it.