The invention discloses a local program stream insertion method in a broadcast system and a broadcast system. The method for the local base station to be inserted into the local program stream in the broadcast system comprises steps of receiving a first signal emitted from a big broadcast tower, wherein the first signal comprises public program streams in the coverage range of the big broadcast tower, demodulating the first signal to a modulation signal level, mapping the local program stream into a complex number symbol, and performing phase rotation on the modulation signal based on the complex number symbol to obtain a second signal. The technical scheme disclosed by the invention adopts a cooperation space time coding scheme forwarded by relay rotary, which inserts the local program stream into the public program streams emitted by the big broadcast tower and transmits the public program streams with the local program stream being inserted to a user terminal in the coverage range of the local base station. The invention not only saves the time frequency resource module, but also enables the user terminal to adopt an identical demodulation algorithm to demodulate the received public program stream and the local program stream, and simplifies the complexity of reception and processing.