Electrocardiosignal(ECG) cardiovascular system for short. It serves as a kind of response to electrophysiological processes for depolarization and repolarization. It contains ubstantial physiological including cardiac function, breathing function, cardiac arrhythmia etc[1]. ECG is an effective method of diagnosing cardiovascular and cerebrovascular diseases in medical science. Therefore, the development of ECG signal acquisition system is important in both auxiliary medical diagnosis and scientific research[2] So far many models of ECG signal acquisition system have been developed. One is created by Baoquan He's group[3] using National Instrument Company's DAQ and LabVIEW virtual instrument technology. However, DAQ in this system is relatively expensive and needs separate configuration 4] [5l Moreover, its design is based on industrial safety standard. Therefore, this development is inconvenient and inappropriate for generalization[6]. Another kind of system samples signal directly through the sound card on PCs. The sound card itself has capability of a date acquisition system. Because it has both A/D and DA conversion functions and some other advantages including low cost, good compa stable performance, flexible application and easy update for drivers. Besides, a sound card sends data via DMA(Direet Memory Access which greatly reduces CPU utilization 171 Generally sound cards can reach an accuracy of 16-bit or 32-bit degree of AID conversion accuracy, higher than an usual 12-bit AD card and thus precise enough for most engineering measurement. However, the sound card has its own limitation: it only appropriate for sampling signal in audio range(20Hz 20kHz but not for DC signal and slow signal. Sampling ECG signals sounds cards directly may lose low-frequency components of information that could be helpful to medical diagnosis due to the low frequency of ECG signals, mainly ranging from 0.01Hz 100Hz[8], and most of the energy concentrates in 0.05Hz40Hz. Instead, we provide a design of an ECG signal acquisition system based on sound card and standard amplitude modulation. It can make the sound card adapt to ECG signals sampling.