Tuning a Guzheng, a traditional Chinese zither, can be achieved 2 ways. The first way involves adjusting the tension of its strings to produce the desired pitches. The second involves moving the bridges to fine tune the string.
Here are general steps for tuning a Guzheng:
Understand the Tuning: The Guzheng has movable bridges, and each string is traditionally associated with a specific note. The standard tuning for a 21-string Guzheng is the D major Pentatonic scale: D, E, F#, A, B. This pattern repeats in order over the entire instrument. There are alternate tunings to achieve different keys and scales but we will be using standard ‘D major’ tuning for this example.
Get a Tuning Wrench: In order to tune the strings of a Guzheng you will need a tuning tool, this is a wrench designed to fit the tuning pegs of each string. These wrenches are always included with the purchase or rental of a Guzheng.
Identify the Strings: Each string on the Guzheng needs to be tuned to a specific pitch. The thickest string is ‘D’ , and it follows the pattern ‘D , E , F# , A , B, D, E, F# , etc’ To help the eye see the 5 string sets the ‘A’ string is usually a different color . Identify the strings, and the ‘A’ string pattern so you know which string you are tuning to which pitch.
Tune from Low to High: Start tuning from the lowest-pitched string and move to the highest. Insert the tuning wrench and turn the tuning pegs clockwise to increase tension (raising the pitch) or counterclockwise to decrease tension (lowering the pitch). On the thinnest strings (highest pitched) be careful and turn the tuning wrench slowly to avoid breaking a string.
Use a Chromatic Tuner: There are smart phone apps that are tuners. Additionally you can buy a small digital chromatic tuner, which can be more accurate. You’ll need to get the tuner close to the instrument, you can put it on a music stand. Some tuners have little clips like the picture above – you can clip it to tuning box. As you tune the string, you’ll need to continuously pluck the string as you watch the tuner. All tuners have some kind of light or signel when you are right on a pitch.
Bend / Stretch The Strings, Check Tuning Again: Once you have tuned all the strings, the next step is to gently bend the strings by pressing down on the string towards the floor. After stretching the strings some may go out of tune again, this is normal and you’ll have to go through all the strings again and tune them to pitch
Adjusting The Bridges: 
Sometimes you will need to fine-tune the pitch of individual strings by moving the bridges slightly. The bridges are moveable and can be adjusted to refine the intonation. Lift the string up with your right hand and grab the bridge with your left hand thumb, index and middle finger to slide it to the left or right to fine tuning. Moving the bridge to the right increases the pitch, moving to the left lowers the pitch.
Repeat as Needed: Go through the tuning process a few times if necessary.
Now that you know the basics of how to tune a Guzheng, remember that it may take some practice. Also it is important to be patient. If you’re unsure about tuning the instrument yourself, consider seeking help from a more experienced player or a professional instrument technician.