Gavin Calver will complete his duties alongside his current role at the Evangelical Alliance.
The SHPG is responsible for organising the Spring Harvest event, coming up with themes, finding speakers and planning the programme.
On accepting the role, he said: "Spring Harvest has a wonderful history and I want it to be a place of real Evangelical unity where many different Christian groups can come together to worship our amazing God and be inspired to change our world for Him.
"I also want us to innovate and model things at our larger gatherings that can then be used to serve the local church on the ground."
Calver is the son of one of the festival's founders, Clive Calver.
The one-week ecumenical event was started in 1979.
Current Chairman, Malcolm Duncan, has come to the end of his five year term. He said that he was "delighted" with the new appointment.