According to The Wall Street Journal, the technology giant is working with broadcast satellite provider Dish Network on the initiative, which would use elements of Google's Android operating system.
The new software would enable users to locate shows on satellite TV platforms and access online video content from sites such as the Google-owned YouTube. Viewers would also have options to personalise their lineup of programming and content.
Google already has a close relationship with Dish Network, which is a primary partner on its Google TV Ads service. The two companies are now running tests of the new search software among a "very small number" of Google employees.
However, it is thought to be unlikely that the technology will launch on to the commercial market in the near future.
Rumours of a possible Google move into the set top box software market date back to 2007, but nothing has actually materialised so far.
Should a Google TV Search function launch in the US, it would compete directly with the Clicker online video search engine, which has integration deals with set top box firms Boxee and popbox.
A Google spokesman said that the company does not comment on speculation or rumour.