Abstract: To explore the plasma jet to K9 optical, through the bending test and the indentation scratches test the mechanical properties of the processed K9 optical were studied. Firstly, surface properties of K9 glass/diamond materials were controlled of the K9 optical by cold plasma assisted cutting machining. And then a universal testing machine was used to test the bending strength of the plasma-treated quartz glass rod by three-point method. Finally, the critical loads of elastic-plastic transition and brittle transition are obtained by indentation and scratch test. The experimental results show that cold plasma jet for brittle materials the properties influence can be kept over 20 hours. During the loading process, the shear force and positive pressure of K9 glass treated by cold plasma are relatively stable, the friction coefficient fluctuates between 0.09 and 0.12, and the change is not obvious. And cold plasma jet for K9 glass/diamond materials friction pair can reduce the elastic-plastic transition of K9 optical critical load, ductile brittle fracture occurs when ductile brittle stress is delayed, reinforced material plasticity and reduce its brittleness.