  The performance of the method of angular moments on the $\Delta\Gamma_s$
determination from analysis of untagged decays $B^0_s(t),\bar{B}^0_s(t)\to
J/\psi(\to l^+l^-)\phi(\to K^+K^-)$ is examined.
  The results of Monte Carlo studies with evaluation of measurement errors are
presented.
  The method of angular moments gives stable results for the estimate of
$\Delta\Gamma_s$ and is found to be an efficient and flexible tool for the
quantitative investigation of the $B^0_s\to J/\psi\phi$ decay.
  The statistical error of the ratio $\Delta\Gamma_s/\Gamma_s$ for values of
this ratio in the interval [0.03, 0.3] was found to be independent on this
value, being 0.015 for $10^5$ events.
