The beam offset in rectilinear mobile optical communication is investigated thoroughly, and the relation between mobile distance and spot radius, optical receiving power and the relation between angle offset and optical receiving power, image offset are presented. The experiments on optical receiving power are done at the rectilinear orbit with immobile optical transmitter and mobile optical receiver,and with mobile optical transmitter and immobile optical receiver . The space light receiving performance is compared between big aperture optical fiber and solid optical taper. The optical taper is presented as the space light coupling receiving component. The result of the experiment shows that the solid coupling optical taper can receive the focused light signal effectively when the beam is deflected, and suitable to the rectilinear mobile wireless optical communication with the mobile distance scope of 80 m.