The full name of bowstring instrument is bass reform erhu. After the founding of the People's Republic of China, we tried to develop a national orchestra to solve the bass part of the orchestra. Different shapes. The shape is an enlarged version of the erhu, with the shaft on the barrel side, fingerboard and four strings. The side of the barrel is covered with oval python skin, and the strings vibrate and sound on the skin. The bow is out of string. The pitch of the four strings is E 1A 1DG, and the range is 17 degrees. The actual pitch is eight degrees lower than the notation. The performance and effect are slightly stronger than that of the low beard, similar to that of the double bass.