Frequency stability of two independent lasers with the same model is measured by using beat frequency technology. By using the theory of beat frequency, frequency stability of the beat signal is deduced, which can be expressed by the sum of squares of the frequency stability of the reference laser and the measured laser. From the above relationship, the frequency stability of measured laser with the same model with reference laser can be obtained. Two independent lasers (TLB-6017) with the same model produced by New Focus company are used in the experimental measurement, and the results show that the frequency stability of the measured laser is about 1.36×10-8 and the frequency shift is 5.1 MHz at the averaging time of 1 s. Frequency stability is in the same level with the technical specification (frequency stability is about 1×10-8 and frequency shift is about 5 MHz at the averaging time of 1 s), and the relative error of frequency shift is about 2%. The provided method avoids conventional limitations which need a higher stability laser as reference laser.