Abstract: In order to obtain the best operating parameters for preparing slightly acidic electrolyzed functional water (SAEFW), a four-factor central composite design was adopted to investigate the effects of voltage (U), hydrochloric acid solution flow rate (QH), concentration (CH) and water flow rate (QW) on the available chlorine concentration (ACC), pH value, oxidation-reduction potential (ORP) and electrical conductivity of SAEFW. The results indicated that the ACC was affected significantly (p<0.01) by the processing factors, such as QW, U and CH. It was noticeable (p<0.01) that the factors QH, CH and QW influenced the pH value of SAEFW. QH, CH and QW obviously affected (p<0.01) the ORP value and the electrical conductivity of SAEFW. The variations could be well described by linear or quadratic polynomial models. The determination coefficients of ACC, pH value, ORP and electrical conductivity are all more than 0.95. The best operating parameters for manufacturing SAEFW by generator were 4.4 V of DC voltage, 1.04L/h of hydrochloric acid flow rate, 2.8% of hydrochloric acid solution concentration and 210 L/h of water flow rate. The criteria of SAEFW were available chlorine concentration (32±2) mg/L, pH value 6.40±0.1, ORP (920±10) mV and electrical conductivity (1130±30) μS/cm. The experimental results showed that the proposed method could obtain the best operating conditions for manufacturing the SAEFW.