An automatic self-calibrated oscillation method and an apparatus using the same are provided. After a static time tuning (STT) table and a run time tuning (RTT) table have been established, the apparatus converts an output clock signal to generate a current RTT value at every predefined time and then compares the current RTT value with a reference RTT value generated in response to a STT value of the STT table, or with an interpolated result generated in response to the reference RTT value to generate a deviation value. Thus, through the deviation value, the output clock signal may be calibrated to address the target frequency without the assistance of external reference clock unit or locked loop unit after the STT table and the RTT table are established.