The dynamic viscoelastic properties of 30 wt% solutions of styrene (S)‐butadiene (B) radial (star) block copolymers were measured to investigate the effect of deformation history. The block structure for SBH1 examined was(S‐B‐)mand that for BSH1(B‐S‐)n,wheremandnare about 5. The solvents used were chlorinated diphenyl (KC4) and dibutylphthalate (DBP); the former is a good solvent for both polystyrene (PS) block and polybutadiene (PB) block, and the latter is a good solvent for PS block and a poor solvent for PB block. Both storage modulusG′and loss modulusG″vary little with maximum strain amplitude(γ0)for the solutions in KC4, or for those in DBP at 80°C. On the other hand,G′,andG″depend significantly onγ0for solutions in DBP at temperatures lower than 60°C, implying that the former systems are homogeneous solutions and the latter contain microdomain structure.G′andG″of DBP solutions of SBH1 are independent ofγ0forγ0⩽0.03,G′decreases andG″increases in the range0.04<γ00.1.This increment inG″with increasingγ0is attributed to a domain structure existing in the solution which will be broken down gradually; correspondingly the relaxation time will be shortened. Reformation of the micro‐domain structure takes about 40 min at 60°C.