Walker follows the director of cricket Matthew Maynard and Jamie Dalrymple out of the Swalec Stadium door.
Maynard resigned on Wednesday after being told he was going to be demoted to a coach with Colin Metson taking over as managing director.
Last season’s captain Dalrymple has also resigned having been replaced as skipper by South African overseas signing Alviro Petersen.
Walker has left after admitting he had serious concerns on the impact of the team.
In a statement, Walker said;
“After two years in the post, I have decided to step down as President of Glamorgan County Cricket Club,.
“Much has already been reported on the proposed changes in the running and structure of the team.
“I have serious concerns about their likely impact. My standing down now will give the Chairman and officers of the club sufficient time to recommend a suitable replacement to the membership.
“Throughout my period in office the loyal fans of Glamorgan CCC overwhelmingly gave me their support.
“They deserve, and will expect the new President to continue to speak and act on their behalf.
“Next summer, I pray that whatever Xl takes the field wearing the daffodil, rewards their efforts.
“Even if they don’t, I shall be there supporting them.”