This article is based on several nouns about transmission performance such as limiting positions, manipulation angle, transmission angle and mechanical advantage. In order to analyse the transmission performance of the coupler-driven and crank-output linkage mechanism, this article has developed an index called Transmissivity of Mechanical Advantage (TMA) for designers, besides this useful index, this article has identified a new noun as Total Transmission Coupler Point, that means after acting a force on the same direction of coupler point moving instantly, then the output force on the crank will act on it¡¦s moving direction and make the Transmissivity Index be the best as 1. For the designers of the coupler-driven linkage mechanisms, the transmission performance and the position where the force acts on involves to coupler curves very much. Based on the result of this research, the designers are able to choose the most proper coupler curves, and the best position of the coupler point would be designed. The designers are able to pick the best one among several similar coupler curves, and also they can certainly get a best range of either the length or the angle of the coupler designed when they were designing the coupler-driven type 4-bar linkage or the Stephenson¡¦s III 6-bar linkage. The applying force must change the direction all the time when a coupler-driven mechanism is driven, and it makes this type of mechanism seems to be uncommon, but it doesn¡¦t mean this kind of mechanism is not worth of application. On the other hand, the short of research about this type of mechanism makes the designers feel helpless when they were trying to analyse the transmission performance of mechanisms were designed. This article develops not only the theorem of analysis but also builds computer programs to help the designers to analyse the transmission performance quickly and correctly