The invention provides an automatic detection method for tuners of a set top box, comprising the following steps: S1: preparing a set top box with different types of tuners; S2: performing wired connection of the HDMI line, the signal line and the power line (12V*2A power supply) in the set top box in the step S1; and S3: sequentially reading and writing I2C addresses of different tuners by usingthe I2C read and write function according to different tuner I2C addresses (I2C protocol, two bidirectional serial lines, one data line SDA, and one clock line SCL) of different tuners. On the basis of multiple types of tuners of some current set top boxes, there is no need to use different software for different tuners. The automatic detection method may achieve the use of the same software, and,at the same time, reduces the time to modify and compile the software again, saves manpower maintenance costs, and speeds up the production process and so on.