By the treatment of lost circulation and drilling fluid overflow in 61-21 well in Mawu formation, a typical gas well with small reserves and with the increasing of drilling fluid lost, two characteristics of higher formation pressure and overflow at wellhead while stopping pump were summed up. It is difficult to deal with the vicious circle of lost circulation, overflow, increase density and lost circulation again. Under the conditions of lost circulation and overflow, it is important to judge rapidly if the problem is in a gas well with small reserves; if it is, flat push killing well is an economical and effective method. The experiences and lessons from the combination of circulation & weight and flat push killing well methods in dealing with overflow of gas well with small reserves could be the reference to the similar wells.