Optically pumped cesium vapor magnetometer generates larmor frequency and needs to get magnetic field values by translation of measured frequency. The precision of frequency measurement is directly related to the accuracy of measured magnetic field values. This paper presents a frequency measurement method for optically pumped cesium vapor magnetometer based on FPGA carry chain. Firstly, using the adder to connect FPGA special carry line into a carry chain, and then based on the principle of time interpolation to achieve the measurement of larmor frequency. Compared with other frequency measurement methods, the proposed method can be realized only by the FPGA programming, and requires no additional hardware cost. The test result of the prototype shows that the system is feasible and the measurement accuracy is high. Thus achieving frequency measurement of optically pumped cesium vapor magnetometer with low cost and high flexibility.