The 31-year-old twice denied midfielder Alan Navarro before Lloyd Dyer somehow wasted a chance late on.
Graham Turner’s men hung on to underline their automatic promotion hopes, while the Dons all but confirmed their promotion, extending their unbeaten run to 15.
In a poor first-half, Dons winger Jemal Johnson had the only chance, forcing Brown into action with a half-volley.
After the restart Brown was on form again to twice thwart Navarro. However, the Dons should have secured their League One status when substitute Mark Wright set up Dyer but he could only curl over.
Wright had a chance of his own in the dying seconds but his effort was hacked away by midfielder Toumani Diagouraga.