hi , can you see the image and told me how I can fix it?
Your X & Y axis are not rigid enough for the cutting forces applied.
When the machine transition from X to Y direction there is a change in rigidity, or lack there of preventing the bit from staying on path. (the machine think its on path)
How can this be fixed?
Check belts & wheels for play. Also check any stepper pulleys in case they are slipping.
I watched the device while it was working, moving around the same place every time!
So I do not think the problem of the wheels
Run a test carve with circles only, in 1" increments, say 1", 2", 3",…,10".
Same feed rate, same depth on all.
Measure all circles in X and Y direction, and diagonally.
Are the measurements consistent/true?
Your X & Y axis are not rigid enough for the cutting forces applied.
Try same test but with cut depth (per pass) 25% of what you used here.
I see your depth of cut is .150.
But what is your depth per pass.
I hope your not trying a full depth cut??
I did . the result is same
I change it to 25% per pass,
the result is same
Then I´d check the mechanical aspects of your machine for any slack/weak points. There are obviously some.
What kind of bit do you use? (As much details as possible please 
)
Haldor is right, inspect the machine. I just finished resolving a similar problem. Turned out that one of the z axis v wheels was loose and that in one “sweet spot” the dust extractor put twisting force on the carriage, pushing the spindle slightly off the cut line as it cut through curves.
My machines are in a classroom where 120 kids each day have a chance to mess with it. They are not malicious, just curious. In the past I’ve found drag chain link taken apart, debris stuck in one or more of the carriages, unsecured wires snagging on a carriage. Once a kid stuck a little 1" scrap cube of wood under the y axis carriage. It would just ride along on the carriage, out of sight, but occasionally, it would vibrate into the way of one of the idler wheels, catch on the belt and ruin a carve.
Repeat your test carve and instead of watching the spindle, watch the movement of the carriages at the places where the anomalies are occurring. I’ll bet you find that something is flexing, catching, or binding, causing the spindle carriage to jerk or jump.
Amana Tool 46018-K CNC SC Spektra Extreme Tool Life Coated Mortise Compression Spiral 1/4 D x 1 CH 1/4 SHK 2-1/2 Inch Long 3 Flute Router Bit
I’ll do
Have you tried changing the rpm on your bit? I’m wondering if you may be fighting some resonance points.
I’m using Dewalt 611 at the lowest setting (1)
I would definitely try a higher setting.
Something is loose, check all grub-screws