can anyone help me..? I am using MAX30100 with arduino, and my expectation is i can to process the ADC as usual (0-1023), but I do not understand the signal processing. Has anyone used the MAX30100 here before? if so, how to process the ADC's wavelength?
This device does most of the low-level processing for you. The measurements and processing to compute pulse rate and oxygenation are done on the board. You need an I2C library (the 'wire' library is one), and a MAX30100 library (there appear to be a few of them).
Here is a link to the MAX30100 datasheet which has all of the low-level detail you might ever want to know about how this chip does what it does.
There is at least one tutorial for this device; I found this one that seems to make sense to me as I read it (and I have never used this device). It tells you which MAX30100 library the author used (there are a few) and provides some sample code.
If it were me, I'd follow the tutorial (the one I linked or some other one) to get something working quickly, and use that knowledge to get your own project going. If you have questions about the device itself, you can find answers in the data sheet.