A novel design of a noncontact,low-cost magnetic rotational encoder is presented in this paper,which is a robust device,resistant to dust,oil and can be used in harsh environment.It includes three key parts: 1)Time grating,which is a base of the sensor;2)magnetic ring,which has 12 poles;3)TMR,which is magnet sensitive element.Base on Time grating,making use of TMR detect the variation of magnetic-flux and produce a signal that contains angular position information as the magnetic ring rotates together with the shaft.After processing,the measurement of angular position can be realized.At last,the performance of the sensor we designed is tested,the original error with the respect to theoretical angle is ± 0.04°,the resolution is 0.072°.It combines advantages both magnetic sensors and Time grating,realize higher accuracy of measurement and resolution just use general mechanical parts.