The macroalgal blooms have occurred in the Yellow Sea every year since 2007, resulting in environmental damage and huge economic losses. According to the monitor data in the field, we found the green tide disappeared in the Qingdao Sea area. In this paper, we used the satellite remote sensing, marine surveillance and laboratory experiments to explain the drifting process, the dynamic change of coverage areas and the floating macroalgal physiological characteristics along the coast of Qingdao in 2014. The results showed that the green tide began to affect Qingdao coast at the late May; from mid-June to the early July, the impacted area of the macroalgal blooms expanded quickly and reached its peak value; afterwards, the blooms decreased gradually. In-situ mesocosm experiments showed that the growth rate of algae biomass was about 2%/d, the floating algae were of light green or yellow, partly white. Most of the Ulva species had the structure of sacs, some were tubular and pleated. The intervals of the macroalgal cells increased and a part of them presented granulation. The fluorescence activity of Ulva algae in the Qingdao sea area was less than 0.52, and the chlorophyll content was low, about 0.3 mg/g. This study showed that the floating Ulva macroalgae were in a stage of degradation.