The relationship of the period T-s and the wavelength lambda (s) of spiral waves with the control parameters is systematically studied with the Belousov-Zhabotinksy (BZ) reaction in a spatially extended quasi-two-dimensional system. Our experiments indicate that T-s and lambda (s) not only rely on the concentrations of sulfuric acid and sodium bromate, as indicated in the previous work [A. L. Belmonte, Q. Ouyang, and J. M. Flesselles, J. Phys. II 7, 1425 (1997)] but also have strong relation with the concentration of malonic acid (MA). With the influence of the concentration of MA taken into consideration, a revised power law of spiral waves is suggested, which is qualitatively in agreement with early works of numerical simulations and theoretical analysis.