Incremental　photoelectric　encoders　inevitably　have　undesirable　factors　such　as　quantization　errors,　manufacturing　defects　and　wear　and　aging,　which　bring　noise　to　the　speed　estimation.　The　previous　speed　measurement　methods　of　motor　rotors　all　use　the　differential　method.　The　differential　method　amplifies　the　noise　and　introduces　a　time　delay　to　the　controller,　which　are　extremely　detrimental　to　the　controller　design.　This　article　aims　to　use　Nonlinear　differential　tracker　(NDT)　to　estimate　the　rotor　speed　of　a　DC　servo　motor　without　increasing　hardware　resources,　and　to　provide　reliable　speed　feedback　information　for　the　controller.　Given　the　rotor　position　information　of　the　motor,　this　method　can　quickly　track　the　derivative　of　the　input　position　signal,　avoiding　the　problem　of　noise　amplification　caused　by　other　methods,　and　the　algorithm　is　simple　and　easy　to　implement　on　a　microprocessor.　Simulation　and　experimental　results　verify　that　this　method　can　effectively　reduce　noise　interference　and　provide　relatively　smooth　speed　estimation　information　with　less　jitter.　It　is　of　great　significance　to　the　design　of　the　control　system.　©　2022,　The　Author(s),　under　exclusive　license　to　Springer　Nature　Singapore　Pte　Ltd.