With the different quality ratio of 1:0, 1:1, 1:2, 2:1 and 0:1 (drying basis), co-precipitation protein was prepared from tilapia muscle and defatted soybean meal by pH-shifting. Tilapia protein isolate (FPI), co-precipitation protein (CoPP-1:1, CoPP-1:2, CoPP-2:1) and soybean protein isolate (SPI) of 18 kinds of protein powder were prepared by freeze drying. Its basic components, solubility, whiteness and amino acid composition were analyzed. Results showed that the content of the crude protein of co-precipitation protein was above 80%, and fat content was less than 1.07%, with being more than or near to the crude protein and fat content of FPI and SPI. The solubility of co-precipitation protein was poor at pH 4.0-6.0, it increased when the pH value was below 4.0 or above 6.0 and reached the maximum value at the extreme pH environment. Relatively, the solubility of CoPP-1:1 and CoPP-1:2 at pH 7.0-8.0 was higher than that of CoPP-2:1 and FPI, but both of them were lower than the solubility of SPI in water and the whiteness of co-precipitation protein was better. The results showed that the composition of CoPP-1:1 and CoPP-1:2 are closer to SPI. SPI mainly consists of water soluble globulin, and has higher solubility in water. The composition of essential amino acid of co-precipitation protein was complete, and the total essential amino acids were about 42 percent of total amino acids, which belonged to high quality protein. Therefore, pH-shifting process could extract high protein content and high nutritional value of co-precipitation protein.