Abstract: Analysis on the effect of safety input in coalmines with theory of "Rheology-Mutation" shows that the effect of safety input also takes on a characteristic of "Rheology-Mutation" with time going by.Therefore,safety input should be a continuous,ongoing job,not just be a one once for all in the initial stage.What's more,the subsequent safety input should be put in an optimal period of time when unsafe conditions is worsening;the input time can not exceed the warning point of safety mutation at the latest.Only this can the safety rheological period be prolonged.and thus the utility of safety input can be brought into a full play;the inconsistency between the need for safety input in coalmines and the lack of safety input can be alleviated.