Abstract: It is difficult for traditional gear drive to meet requirements of high precision drive of eletro-optic system because of problems of backlash and gap. Based on analysis of technical characteristics of cable and steel belt drive, 1:1 angle measuring mechanism of periscope based on cable drive and 2:1 drive mechanism for electro-optic system based on steel belt drive are designed. Based on optical measurement method, transmission error of cable and steel belt drive mechanism is measured by rotary transformer and theodolite respectively. Results show that transmission accuracy of cable drive can reach minute level, corner error is less than 3.5′ in range of -110°~+135°; while transmission accuracy of steel belt drive can reach second level, angle error is less than 11.9″ in range of -3°~+3°. In conclusion, flexible drive has high transmission accuracy and can satisfy performance requirements of electro-optical system.