Thanks Danny, your idea is nice.
So I decided to write a EA to verify it, and did a simple update for this logic.
1, EMA_high or low is not enough to make sure the position is right to open, so it need a ema with period 15 price is close to above or below it.
2, 5 min is good to generate many trading opportunities but also has some wrong position, so I use the ema period 15 on M15 chart, at least, once it found a position which has two charts to verify its valid.
but I don’t do any stop loss logic in this EA, and it works in 2013, but very bad before it, maybe the data on MT4 is not well