A transmitter optical sub-assembly, includes a prism body, a first lens, and a plug-in. The prism body includes a light inlet end and a light outlet end, the first lens is disposed between the light outlet end and the plug-in, and the plug-in includes a contact end. The contact end is located on a surface that is of the plug-in and that is away from the first lens, a center of the contact end is located on a focus on an optical path of the first lens, and the contact end is arc-shaped for a purpose of a gapless interconnection with an optical fiber, to reduce end face reflection of the contact end. An optical transceiver assembly includes the transmitter optical sub-assembly, and has comparatively small reflection and a comparatively small return loss of an optical fiber end face.