Using a solution of $^{137}$ Cs as a tracer, radioactivity of a $^{137}$ Cs solution is measured by coincidence and anticoincidence counting methods. Sample sources in this study are fabricated by mixing $^{137}$ Cs with tracer, and the mixing ratios are 1/3 and 1/5, respectively in coincidence and anticoincidence methods. Specific activities of a $^{137}$ Cs solution are calculated by means of f-channel low energy threshold level variation and efficiency extrapolation. The results obtained by coincidence and anticoincidence counting methods are 552.78 kBq/g and 554.32kBq/g, respectively on the reference date and the combined uncertainties are 1.60kBq/g and 1.51kBq/g for each method. These two results show a good agreement within the uncertainty range.