The invention discloses a method for switching program source in stream media playing which includes: a program source switching command for switching a current first program source to a target second program source is transmitted to a stream media playing system; after receiving the program source switching command, the stream media playing system continues to collect and play stream media data of the first program source and starts to collect stream media data of the second program source; after effective data of the second program source is obtained, the collection of the stream media dataof the first program source is stopped; at the same time, the stream media data of the second program source is started to play, and the switching from the first program source to the second program source is realized. The invention also discloses a related stream media playing system. By adopting the invention, period without any blank screen is realized during program source switching; besides,when the program source code rate is different after switching, a second encoding process is carried out for the stream media data, and a receiving terminal is not required to be notified to conduct code rate change.