The invention relates to an ORC generator set for self-adaption of heat source change and an adjusting method. The generator set comprises an evaporator, a power unit, a condenser and a shielding pump connected in sequence through pipes, and further comprises an adjusting valve mounted between the shielding pump and the evaporator; and a liquid level meter is mounted on the evaporator. The adjusting method comprises the following specific steps: 1) primary adjustment is performed; 2) if the liquid level is returned to a set value, adjustment is stopped; and if the liquid level is not returned to the set value, and the openness of an adjusting valve is adjusted, the liquid level is not changed anymore, and the step 3) is performed; and 3) secondary adjustment is performed. The generator set can automatically adjust self working conditions along with the parameter change of an external heat source (water vapor), so that parameters of a heat source in the evaporator are corresponding to working medium parameters one to one, and normal and stable work of the whole generator set is guaranteed.