Abstract　

We will discuss the case of the binary black hole system OJ287 which has the major axis precession rate of 39 degrees per period, about four orders of magnitude greater than the precession in binary pulsars. Therefore we may test General Relartivity to the second Post Newtonian order for the first time. In the OJ287 system we determine the spin of the primary black hole as well as its mass. In General Relativity these uniquely determine the quadrupole moment. In the OJ287 system the quadrupole moment can be measured, and one may then perform a test of the so called no-hair theorem. The test parameter q=1 in General Relativity: our determination is q=1+/-0.3. The test may improved to the level of +/-10% in this decade if certain crucial measurements are carried out.