The invention discloses a soft pack lithium ion battery. The soft pack lithium ion battery comprises a shell, wherein a nude cell and at least one built-in pipe of a hollow structure are arranged in the shell, the top surface of the built-in pipe is connected with the inner wall of the shell, and the side surface of the built-in pipe is provided with at least one through hole. The built-in pipe isarranged in the shell, the built-in pipe is provided with a through hole, when in secondary electrolyte injection, an electrolyte injection needle can be adopted to pierce the shell and the top surface of the built-in pipe to enter the built-in pipe, electrolyte is injected into the battery by virtue of the built-in pipe, and then a pierced opening of the shell is sealed by using sealant, so thatthe safety is high, the quality of the battery can also be ensured, the service life of the battery is prolonged, the utilization rate of resources can be increased, and the recycling pressure of theindustry can be alleviated. Compared with the existing method for switching a tab and re-sealing the secondary injected electrolyte, the operation method and equipment requirement of the soft pack lithium ion battery of the invention when in secondary electrolyte injection are simple, and the soft pack lithium ion battery is convenient to use widely. The soft pack lithium ion battery is applied to the technical field of batteries.