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The no-insulation (NI) winding technique drastically enhances the thermal stability of REBa2Cu30y (REBCO) coils. Even if a larger current than a critical current carried in NI REBCO pancake coils, the coils would not burn out. So far, many NI REBCO pancake coils showed a "self-protecting" characteristic in experiments. However, most of these experiments have been done under a low magnetic field or cooled by liquid nitrogen. Under these conditions, a huge electromagnetic force does not occur after an NI REBCO pancake coil transitions into a normal state.Recently, the NI winding technique has been applied to high field magnets, such as NMR and accelerators. Under a high magnetic field, a huge hoop stress are generated after one NI REBCO pancake coil constituting a high field magnet by stacking reaches to quench. The huge hoop stress causes the delamination of REBCO coated conductors. That is, the quench protection condition of high field NI REBCO magnets is decided according to the mechanical condition, even though the magnets show a high thermal stability. In this paper, 3 simulation models for NI REBCO pancake coils are compared, and then the mechanical condition is discussed for a quench protection through an electromagnetic, thermal, and mechanical simulation of multistacked NI REBCO pancake coils for high field generation.