To improve product family design methods for mass customization currently, scale-based modular method for product family design is proposed. On the basis of it, a web-based customization product design system is built. Three processes are included in the system: modeling product family, customizing individual product and estimating cost. Key technologies used in the system are studied on focus that include modular design, scale factors design, tabular layouts of article characteristics (LAC), Case-Based Reasoning (CBR), parametric CAD (SolidWorks) and so on. Finally, taking MK2110 internal grinder as an example, the web-based customization design system is set up.