The 49-year-old will drop to 51st in the Official World Golf Rankings after tying for 28th at the HSBC Champions in China over the weekend.
Mickelson was as high as 17th in the rankings earlier this year after winning the AT&T Pebble Beach National Pro-Am, but his performances have steadily declined since.
After finishing tied for 18th at the Masters in April, the five-time major winner has missed the cut six times and hasn't finished higher than 28th.
Mickelson's record streak in the top 50 is more than seven years longer than the next best, which belongs to Ernie Els. Rory McIlroy, who finished first at the HSBC Champions, now holds the longest active streak of just over 11 years.