Reducing or even breaking the chain of Covid-19 virus infections during a pandemic is important. The techniques that are encouraged are mandatory hand washing, social distancing, and mandatory wearing of masks. Wearing masks is urgent, therefore requiring people to wear masks is the right policy. This study aims to detect people who use masks or do not use masks by applying the Viola Jones method. In this study, modification of the tresholder algorithm was carried out by applying a mask thresholder for optimization of facial segmentation. Meanwhile viola jones was built by combining several concepts of Haar Feature, Integral Image, AdaBoost, classivier Cascade into a main method for detecting objects. The performance of the proposed method for face detection has an accuracy of 95%, a precision of 94.73%, and a recall of 100%. 5. The masked face detection test has an accuracy of 94%, precision 100%, and recall 90.90%