Quantitative relations between parameters of two dimensional transonic-supersonic nozzle flow of circular throat are expressed through the form of "characteristic curves without reverse pressure gradient". These relations can be regarded as a guide for design of laser nozzles of big throat curvature in rapid expansion without reverse pressure gradient. To Combine with the associated calculation program of transonic-supersonic nozzle contours in which the value of five parameters can be changed, it is possible to select nozzle contours of this type on computer. These characteristic curves can also be used as a reference, forh estimating character of reverse pressure gradient of this type of nozzle obtained by other ways.