Objective To develop a sensor for measuring oar force in rowing real time. Methods A horseshoe sensor was developed to be easy to fix to the thole of gig. The mount of sensor does not change any structure of the gig. The rowing of athletes will not be obstructed by force measurement. Results The linear load-strain relation was measured in the laboratory experiment. Such linear relationship ensures that the electrical output of the sensor is proportion to the oar force exerted by athletes.