Lightweight technology is to transform the discarded materials, such as dredged silt, construction waste soil, waste foam plastics, industrial waste fly ash, waste gypsum, etc., into lightweight soil. This kind of soil has been utilized comprehensively, which can produce good economic benefit, environmental and social benefits. In order to further investigate the properties of mixed lightweight soil, this paper uses indoor test method to study the recycled sludge lightweight soil samples prepared from the construction waste soil by mixing with EPS particles and cement according to certain mass/volume ratio and cured in standard curing conditions. The strength properties and failure mode are analyzed using the direct shear test and unconfined compressive strength test, and the effect of curing period, cement content, EPS particle fraction, etc., on the strength and failure mode is analyzed.