Abstract: The internal temperature of composite gas cylinders usually experience a temperature increment effect during the rapid gas-filling process of compressed natural gas (CNG) and hydrogen. As a result of severe temperature elevation, it would lead damage to the wound layers of the composite cylinders and threaten the safety of the vehicle gas supply system. For the sake of boosting the driving mileage of CNG cars, and the popularization and application of 35 MPa CNG gas cylinders and basalt fibers, this paper built a two-dimensional CFD model for the rapid temperature rise of CNG cylinders, and numerical simulations of 35 MPa basalt fiber reinforced composite cylinders during the rapid charging process were applied. Under the set conditions with 45 MPa filling backpressure, 293 K environment temperature and 2MPa inner pressure of gas cylinders, the results show that 5 minutes rapid gas inflation would result in the maximum gas temperature reaching 333 K (60 ℃) and a 40 K temperature increment, which met the requirements of ISO 11439 – 2013" Gas cylinders high pressure cylinders for the on-board storage of natural gas as a fuel for automotive vehicles". Furthermore, according to the simple variable method, fast filling time, ambient temperature and pressure inside gas cylinders were changed, respectively. It is concluded that under the setting conditions and the requirements of ISO11439 – 2013, the fastest filling time and the highest ambient temperature are 100 s and 305 K ( 32 ℃) respectively, while the gas pressure inside the cylinders meets the standard requirements . Therefore, the gas-filling speed of 35MPa basalt fiber reinforced composite gas cylinders in hot environments should be slowed down appropriately to ensure the safety of gas cylinders for long term use.