So, when i plug the MOSI from arduino to the chip, it results nothing. But, when I unplug it, it results random number. So I concluded from that, I have no problem with the hardware.
That conclusion is wrong. The SPI interface consists of at least 4 signal lines: SS (slave select, sometimes called CS for chip select), MOSI (master out, slave in), MISO (master in, slave out) and SCKL (serial clock). All of them have to be connected for the SPI to work. Make a photograph of your setup and post it. Also provide a link to the datasheet of your AFE4490. Do the same for the used libraries.
pinMode (SCLK, INPUT);
SCLK is an output, not an input.