Oxygen analyzer is oxygen analyzer is a measuring instrument for oxygen levels in a gas. In the health sector, the oxygen analyzer is used to measure oxygen gas levels in oxygen tube, medical gas outlet, oxygen therapy device, Continuous Positive Airway Pressure (CPAP), and ventilator. Oxygen analyzer that exist now still using 7segment as the display that have disadvantages like wasting place at the display that have character limitation. Based on this case, it needs oxygen analyzer with LCD display that can displays any kind of character and more efficient in making of it, so the writer want to make oxygen analyzer with LCD 16x2 as a display. This research intending to make oxygen levels from atmega8-based oxygen analyzer with LCD 16x2 as the display and helps medical staff and technician to know and measure oxygen level in the central medical gas with more faster and efficient due to LCD display. This research using Microcontroller ATMEGA8 that uses RISC (Reduce Instruction Set Computing) technology where program run faster because it just need one cycle hour to execute one program instruction. Based on measurement on oxygen analyzer in RSUD Wonosari obtained an error value, 1,68% in oxygen level 21%, and -0,11% in oxygen level 90%. From the measurement results and analyzing then it can be concluded that the tool works well because error value is under 5%.