A sun tracking method is disclosed. The method can track the position of sun continuously, without the need to install an optical sensor, to calculate a sun-tracking solar orbit function, and to calibrate the mechanical structure periodically. The method comprises the steps outlined below. (A) A motor of an attitude control device is driven for changing attitude of a photovoltaic cell device to sense and record a short-circuit current by a short-circuit current measuring device directly or in cooperation with the switching behavior of a switch power unit of a maximum power tracking control device, or to sense and to record an output power by a power measuring device. (B) A maximum value of the short-circuit current or the output power is calculated. (C) The motor-driving device is driven for modulating the photovoltaic cell device to an attitude corresponding to the maximum value of the short-circuit current or the output power.