This paper presents an algorithm using Slope Vector Waveform (SVW) for ECG QRS complex detection and RR interval evaluation. The algorithm consists two parts of operations. They are variable stage differentiation and non-linear amplification. Variable stage differentiation is used to obtain the desired slope vectors for feature extraction, and the non-linear amplification is used to improve signal-to-noise ratio Results show that, SVW provides excellent QRS detection even if the signals are contaminated with noises. The SVW algorithm is less computationally involved. This makes it ideal for a widely range of machine diagnosis applications, particularly, embedded real-time ECG monitoring.