The invention provides a method for automatically detecting tuner voltage. The method comprises the following steps: step 1): according to the different types of signal polarization modes received by a set top box, selecting the test range of the tuner voltage, and setting the lowest test voltage value; step 2): testing, and recording the current signal strength and quality; step 3): judging whether the current voltage exceeds the voltage range of this type of the signal polarization mode, if not, adding 0.1 v to the current voltage, and returning to the step 2), if so, going to the step 4); step 4): judging the voltage value of the tuner corresponding to the strongest signal, and storing the voltage value; and step 5): displaying the range of the voltage value while the signal received by the tuner is the strongest.