Indonesia is an archipelago located at three earthquake belts. This condition cause an earthquake can occur anytime and threaten human life. A quick and accurate early warning system by using the seismic wave data processing is required so, the number of victims affected by the earthquake can be shortened. Here, ADXL335 accelerometers are used as seismic sensors with an Arduino minimum system. The results show that when the first earthquake’s vibration occurs, P wave data detected by the ADXL335 sensor is successfully buffered, calibrated, transmitted and displayed on the server. When there are errors on the transmission, server will request for retransmission. The alarm of the earthquake early warning system will be activated if there are at least three sensors from different locations successfully transmit P wave data with the same scale. This is needed to prevent fake seismic waves.