Water contamination has negatively impact on the needs of everyday life in the form of changing dissolved oxygen concentration, which is one of water pollution indicators. This paper presents a simple biosensor using amperometric electrodes for observing the changes of dissolved oxygen production rate in the solution. The measuring process is implemented using the biochips G which is connected with a biosensor module and electronic circuit to detect the changes of dissolved oxygen production rate (pO2) directly in real time measurement. Initial test was completed to observe the biochip response to the different oxygenated water solution of 50% and 100% concentration. A light and dark experiment with ON/OFF phase of 20 minutes illumination period was realized to stimulate the green algae Chlorella vulgaris photosynthesis process to produce dissolved oxygen (DO) rate. The measurement results show Biochip G using algae Chlorella vulgaris response to environmental changing conditions in the form of relationship between output voltage and DO rate the solution.