The invention discloses a process for preparing low-sugar mixed jam, which comprises, by mass, 20-25 parts of pawpaw, 10-15 parts of grapefruit, 10-15 parts of xylitol, 2-5 parts of pectin, 3-5 partsof lemon juice, 1-2 parts of potassium sorbate and 100-150 parts of water. According to the invention, the jam is prepared from fruits with extremely low sugar contents, the peel of the fruits can befully utilized, pectin is extracted to be used in preparing the jam, and xylitol is utilized to replace white sugar, so that the jam can be used for people with hyperglycemia and even diabetes while the original sweetness is kept; and a beating device in the process drives four peripheral slave rotating shafts provided with beating blades to rotate at a high speed together to beat the fruits through a main rotating shaft provided with beating blades, so that the beating efficiency is high, the beating time is greatly reduced, and the beating thinning degree of the fruits is high; meanwhile, after the beating is finished, the peel and the seeds are filtered and separated, and the fruit pulp which is mixed with the skin and the seeds is completely separated through a spin-drying mechanism, so that resources are saved; the whole device is convenient to move through a support moving mechanism which is convenient to operate.