North Tehran Fault (NTF) is capable of producing earthquakes with the magnitude over 6. One of the most important parameters for seismic hazard assessment is the slip rate. Determining the slip rate requires to find the period of slip. Two OSL samples were collected from the Kan trench in hanging wall of NTF. The trench is 8 m long, and has a maximum depth of about 4 m. For OSL dating two parameters are required, the equivalent to natural dose (De) and annual dose rate. We used single aliquot regeneration method to calculate the De. The radioactive materials (U, Th and K40), moisture content, cosmic rate and other parameters were employed to calculate the annual dose. OSL dated samples provided the age of 19.2±1.4 ka and 5.8±0.6 ka. These dated will be used to determine the slip rate.