Nonenzymatic autocatalytic DNA circuits, capable of exponential signal amplification, exhibit superior amplification efficiency compared to traditional single or cascade DNA amplification circuits, which offer only linear or quadratic signal amplification. However, autocatalytic DNA circuits are currently limited by complicated splitting designs, low autocatalytic efficiency, the need for additional probes, and a lack of universal design principles. Herein, we developed a PCR-like split-free autocatalytic amplification (SAA) DNA circuit with a simple design but extraordinary autocatalytic efficiency for effective biosensing. The SAA system could consecutively perform multiple cycles of a three-step process upon initiation, target recognition, replicating, and recycling, which is programmed to mimic the basic three reaction steps of PCR and constantly yield numerous new split-free target replicates to expedite the whole reaction, ultimately producing an exponentially amplified signal. The PCR-like sigmoidal kinetics, the ability to accurately execute the programmed instructions, and the high autocatalytic capability of the SAA system are demonstrated, which achieves the same target replication as the PCR but without the need for enzymes and precise control of temperature. The SAA circuit, characterized by exponential signal amplification, simple design, and minimal components, offers a promising approach for developing highly efficient universal DNA circuits. This enables the analysis of low-abundance biomarkers with minimal signal leakage, holding significant potential for biochemical research and clinical diagnosis.