The office chair’s supporting ability is important, especially in forward sitting position, because forward sitting position is mostly used in daily work and it is easy to get low back disc lesions for lack of low back support. The four important supporting factors such as concerning seat cushion depth, angle, waist cushion height and angle were tested by orthogonal design. Experimental results showed that comfortable sensation of forward sitting could be perfectly measured by body pressure measuring indicator and subjective evaluation indicator. Discussing is specific and unified as the result of key indicator collected by range method. Proper leaning of seating cushion and slightly lower waist cushion would improve forward sitting comfort compared with normal office chair.