The measurement tool of oxygen saturation (SpO2) in non-invasive way is a tool that functions to count the oxygen saturation with light colour changing method in red LED and infrared without hurting the fingers in percentage unit. SpO2 uses wavelength of infrared (910 nm) and red LED light (650 nm) captured by detection sensor (photodiode) after passing through blood vessel in the fingertip. The data from photodiode are delivered to micro controller of Arduino and then are shown on LCD. In Arduino micro controller, the data are managed and processed to obtain oxygen saturation value. The normal condition of oxygen saturation value is between 85 % until 100 % and the abnormal condition of oxygen saturation value is < 85 %. In the tool testing, the researcher used the testing by comparing the comparison tools that have been calibrated so that the accuracy can be recognized. Based on the tool testing, the result was that the measurement tool of oxygen saturation (SpO2) equipped with alarm for abnormal diagnose worked well and had error value of 2.69169 %.