The invention provides a recycling and harmless treating process for oily sludge and sand. According to a technical scheme in the invention, an apparatus used in the process is mainly composed of a first screw conveyer (1), a pulverizer (2), a washing tank (3), a slurry pump (4), a high-efficiency solid-liquid separator (5), a first gas bag (6), a first residual oil tank (7), a first cooler (8), an induced draught fan (9), a purifying column (10), a circulating pump (11), a cold water system (12), a water pump (13), a second gas bag (14), a second residual oil tank (15), a second cooler (16), an oil water storage tank (17), a light oil tank (18), a third screw conveyer (19), a second slag removing machine (20), a second main driving unit (21), a thermal decomposition furnace (22), a feeder (23), a second screw conveyer (24), a first second slag removing machine (25), a first main driving unit (26), a drying device (27), a safe water seal (28) and a combustion furnace (29). The invention has the following beneficial effects: recycling and harmless treating requirements for oily sludge and sand are met; an oil recovery rate is high; and continuous and stable production is realized.