The invention provides a transmission mechanism of a propeller dynamometer. The transmission mechanism is capable of solving the technical problems of complex structure, low bearing capacity, low stability and high maintenance cost of an existing transmission mechanism. The transmission mechanism comprises a vertical transmission shaft, a horizontal transmission shaft, a shaft sleeve, a support sword-shaped body and a connection body, wherein the vertical transmission shaft is supported on the shaft sleeve through a first bearing, and stretches in the inner cavity of the connection body; the horizontal transmission shaft is supported on the connection body through a second bearing, and stretches in the inner cavity of the connection body; the horizontal transmission shaft is in engagement connection with the vertical transmission shaft through an arc bevel gear; the shaft sleeve is supported on the support sword-shaped body through a third bearing, and penetrates through the support sword-shaped body; and an angle scale is connected to the upper end of the shaft sleeve, and the lower end of the shaft sleeve is fixedly connected with the connection body.