A huge optical luminosity of the supercritical accretion disc and powerful stellar wind in the high-mass X-ray binary SS433 make it difficult to reliably estimate the mass ratio of the binary components from spectroscopic observations .
We analyze different indirect methods of the mass ratio estimate .
We show that with an account of the possible Roche lobe overflow by the optical star , the analysis of X-ray eclipses in the standard and hard X-ray bands suggests the estimate q = M _ { \mathrm { x } } / M _ { \mathrm { v } } \gtrsim 0.3 .
We argue that the double-peak hydrogen Brackett lines in SS433 should form not in the accretion disc but in a circumbinary envelope , suggesting a total mass of M _ { \mathrm { v } } + M _ { \mathrm { x } } \gtrsim 40 M _ { \odot } .
The observed long-term stability of the orbital period in SS433 | \dot { P } _ { b } / P _ { b } | \leq 1.793 \times 10 ^ { -14 } s ^ { -1 } over \sim 28 year period is used to place an independent constraint of q \gtrsim 0.6 in SS433 , confirming its being a Galactic microquasar hosting a superaccreting black hole .