The invention relates to a low-temperature less-alkali pretreatment method for a modified polyester/cotton blended knitted fabric. The pretreatment method comprises the steps of (1) soaking a polyester/cotton blended knitted fabric in a low-temperature pretreatment composite preparation liquid which is 1: (7.5-30) in bath ratio, rapidly increasing temperature to 65-70 DEG C, adding 2-2.5g/L of 100% hydrogen peroxide, and preserving heat for 60-90min to obtain the blanched fabric; and (2) soaking the blanched fabric in a glacial acetic acid solution, heating to 45-55 DEG C, preserving heat for 10-15min, neutralizing by acid and discharging liquid, sequentially washing by using hot water of 80-90 DEG C, warm water of 50-60 DEG C and cold water, and drying the fabric. The low-temperature pretreatment process simplifies technological process and shortens processing duration on one hand, and also lowers processing temperature, avoids a plurality of washing and drying processes, and greatly improves production efficiency.