A catalogue of light curve solutions of contact binary stars has been compiled .
It contains the results of 159 light curve solutions .
Properties of contact binary stars were studied by using the catalogue data .

As it is well known since Lucy ’ s ( 1968a , b ) and Mochnacki ’ s ( 1981 ) works , primary components transfer their own energy to the secondary star via the common envelope around the two stars .
This transfer was parameterized by a transfer parameter ( ratio of the observed and intrinsic luminosities of the primary star ) .
We proved that this transfer parameter is a simple function of the mass and luminosity ratio .
This newly found relation is valid for all systems except H type systems which have a different relation .

We introduced a new type of contact binary stars : H subtype systems which have a large mass ratio ( q > 0.72 ) .
These systems show highly different behaviour on the luminosity ratio - transfer parameter diagram from other systems and according to our results the energy transfer rate is less efficient in them than in other type of contact binary stars .
We also show that different types of contact binaries have well defined locations on the mass ratio - luminosity ratio diagram .
All contact binary systems do not follow Lucy ’ s relation ( L _ { 2 } / L _ { 1 } = ( M _ { 2 } / M _ { 1 } ) ^ { 0.92 } ) .
No strict mass ratio - luminosity ratio relation of contact binary stars exists .