In order to accurately measure the short transverse relaxation time of alkali-metal atoms, three measuring methods are analyzed, which are modified free induction decay method, broadening-fitting method of magnetic resonance response curve and ratio-fitting method of transverse component of the magnetic moment in the rotating coordinate system. The transverse relaxation time of rubidium atom vapor in a cell in the magnitude of 10 μs is measured with the above three methods. Experimental results show that these three methods can reach the precision in the magnitude of 1 μs . Through analyzing the experimental condition, the modified free induction decay method and ratio-fitting method can give accurate transverse relaxation time for atomic magnetometer. And broadening-fitting method can be used to research the relaxation mechanism without light.