The determination of whether the piston of a hydraulic breaker needs replacement can be checked and analyzed from the following aspects:

1. Check the seals at the piston and piston rod interface: If there is any damage, aging, or loosening of the seals, it indicates that the piston may need replacement.

2. Inspect the striking face at the front of the piston: If the striking face at the front of the piston is found to be damaged during use, it may be due to dropping metal debris. In such cases, the piston needs replacement.

3. Check for surface damage on the piston: If there is damage such as wear or scratches on the surface of the piston, replacement should be considered.

4. Inspect the hydraulic system: If there are issues with the hydraulic system, such as blockages in the hydraulic circuit or pump malfunctions, it may affect the operation of the piston. In such cases, inspection and replacement of the piston are necessary.

5. Regular inspection and maintenance: Timely replacement of oil seals is crucial to prevent oil leaks or entry of foreign objects that could cause piston wear.