Reigning Masters champion Murphy, 43, was aiming for back-to-back ranking tournament victories after winning last month’s British Open in Cheltenham.
The Englishman continued his excellent form in China to reach another final, but was punished for any errors he made during an opening session which his opponent dominated with ruthless efficiency.
Williams seized control by winning the first four frames, pinching the third and fourth frames with contributions of 56 and 68 respectively after Murphy had held significant leads in both.
A superb 127 break in frame eight, to go with his six earlier half-centuries, ensured Williams went into the concluding session 7-1 ahead.
He compiled a 122 break in the ninth frame to extend his advantage further and although Murphy won two frames in a row to reduce his deficit to 8-3, Williams took the next two either side of the mid-session interval to create snooker history.