A lever control mechanism of a drain valve of a toilet tank has a lever assembly assembled in the wall of the toilet tank and a lever linked to the revolving shaft of the lever assembly. The lever assembly is connected to a deviator, which is disposed with a drive arm; the drive arm is connected to the revolving shaft. The deviator is disposed with a joint portion and at least a leading hole to limit the lever revolving vertically. One end of the lever is run through the leading hole to rotationally connect to the joint portion; the drive arm is revolved by the driving of the revolving shaft to drive the lever revolved in the fan shaped vertical surface limited formed by the joint portion and the leading hole.