  We investigate the two-particle intensity correlation function of $\Lambda$
in relativistic heavy-ion collisions. We find that the behavior of the
$\Lambda\Lambda$ correlation function at small relative momenta is fairly
sensitive to the interaction potential and collective flows. By comparing the
results of different source functions and potentials, we explore the effect of
intrinsic collective motions on the correlation function. We find that the
recent STAR data gives a strong constraint on the scattering length and
effective range of $\Lambda\Lambda$ interaction as, $-1.8 \mathrm{fm}^{-1} <
1/a_0 < -0.8 \mathrm{fm}^{-1}$ and $3.5 \mathrm{fm} < r_\mathrm{eff} < 7
\mathrm{fm}$, respectively,if $\Lambda$ samples do not include feed-down
contribution from long-lived particles. We find that feed-down correction for
$\Sigma^0$ decay reduces the sensitivity of the correlation function to the
detail of the $\Lambda\Lambda$ interaction. As a result, we obtain a weaker
constraint $1/a_0 <-0.8$ fm$^{-1}$. Implication for the signal of existence of
$H$-dibaryon is discussed. Comparison with the scattering parameters obtained
from the double $\Lambda$ hypernucleus may reveal in-medium effects in the
$\Lambda\Lambda$ interaction.
