Due　to　the　simple　structure,　single-contact　light-emitting　diode　(SC-LED)　holds　promise　for　applications　in　ultrahigh　resolution　micro-displays.　However,　the　required　alternating　current　(ac)　operation　poses　challenges　for　grayscale　modulation　in　image　display　applications.　Therefore,　it　is　of　great　significance　to　develop　a　potential　grayscale　control　technology　for　the　ac-driven　SC-LEDs.　In　this　work,　the　optical　and　electrical　characteristics　of　the　SC-LEDs　are　investigated,　and　an　anomalous　pulsewidth　modulation　(A-PWM)　technology　is　proposed.　In　the　A-PWM　mode,　the　brightness　decreases　with　the　increasing　pulsewidth,　which　is　totally　different　from　conventional　pulsewidth　modulation.　The　carrier　transport　model　and　the　circuit　model　are　established　to　clarify　the　A-PWM　mechanism.　Furthermore,　the　brightness　division　is　carried　out　on　the　basis　of　the　A-PWM,　and　the　human　eye　brightness　perception　model　is　established.　Nonlinear　correction　is　applied　to　align　the　brightness　change　with　the　characteristics　of　human　eye　perception.　This　work　proposes　a　brightness　modulation　method　suitable　for　SC-LEDs,　which　is　expected　to　be　applied　to　ac-driven　nano-pixel　light-emitting　displays.