The Galaxy rotation curve is usually assumed to be flat .
However , some galaxies have rotation curves that are lower than the flat rotation curve .
In our Galaxy the Keplerian rotation of interstellar clouds in the galactic longitude l = 135 \degr was observed .

We use a kinematic approach to derive the rotational velocity of classical Cepheids .
The rotational velocity was calculated from radial velocity and from proper motion .
The derived rotational velocities of Cepheids are between Keplerian rotation and the flat one .
We fit a Galaxy rotation model consisting of a black hole , bulge , disk and halo to the rotation curve .
The density of dark matter halo is at least 60 % less than the value obtained from the flat rotation curve .