We run hydrodynamic simulations which follow the colliding winds structure of the massive binary system HD 166734 along its binary orbit , and show that close to periastron passage the secondary wind is suppressed and the secondary accretes mass from the primary wind . The system consists two blue supergiants with masses of M _ { 1 } \approx 39.5 ~ { } { M _ { \sun } } and M _ { 2 } \approx 30.5 ~ { } { M _ { \sun } } , on a P \simeq 34.538 ~ { } days orbit with eccentricity of e \approx 0.618 . This close O-O binary with high eccentricity is observed through its orbit in the X-rays , where it shows an unusual long minimum close to periastron passage . We use advanced simulations with wind acceleration and prescription treatment of accretion and simulate the entire orbit at high resolution that captures the instabilities in the winds . We find that the colliding wind structure is unstable even at apastron . As the stars approach periastron passage the secondary wind is quenched by the primary wind and the accretion onto the secondary begins . The accretion phase lasts for \simeq 12 ~ { } days , and the amount of accreted mass per cycle we obtain is M _ { acc } \simeq 1.3 \cdot 10 ^ { -8 } ~ { } { M _ { \sun } } . The accretion phase can account for the observed decline in X-ray emission from the system .