The Blues have already added Cesc Fabregas to their squad this summer but now Jose Mourinho wants the Spaniards former Barca team mate Song to join him at Stamford Bridge.
Song left Arsenal in 2012 but has failed to make much of an impact in La Liga and is now available for around £20million, £5million more than Barca paid for him.
Manchester United are also keen on Song who was a key man at the Emirates before his controversial move to Spain.
Chelsea are not willing to cough out £20million for the Cameroon international, who failed to impress at the World Cup, and so will begin negotiations with the Catalan club this week.
Song is desperate for first team football and knows a return to England would enhance his career, however big spending Barcelona are playing hard to get.
If the move for Song fails, Mourinho knows he will have to spend big in order to fill that hole in his team and £40million-rated Paul Pogba is next on the list.
The Blues will have to sell before they buy Pogba but Mourinho doesn’t see that as a worry with the likes of Romelu Lukaku, Ryan Bertrand and Victor Moses all on their way out of west London.