是使能中断，按照你的理解 就是允许

允许。

如果你是stm32初学者，建议你查看STM32固件库使用手册的中文翻译版.pdf
关于这个函数有如下解释：

如果你有一定的stm32基础，建议你直接查看库函数源代码：
这个里面是官方原版解释，如下图：

本帖最后由 叶子心 于 2017-9-7 10:08 编辑

允许USART_IT_RXNE中断。。。
/**
  * @brief  Checks whether the specified USART interrupt has occurred or not.
  * @param  USARTx: Select the USART or the UART peripheral.
  *   This parameter can be one of the following values:
  *   USART1, USART2, USART3, UART4 or UART5.
  * @param  USART_IT: specifies the USART interrupt source to check.
  *   This parameter can be one of the following values:
  *     @arg USART_IT_CTS:  CTS change interrupt (not available for UART4 and UART5)
  *     @arg USART_IT_LBD:  LIN Break detection interrupt
  *     @arg USART_IT_TXE:  Tansmit Data Register empty interrupt
  *     @arg USART_IT_TC:   Transmission complete interrupt
  *     @arg USART_IT_RXNE: Receive Data register not empty interrupt
  *     @arg USART_IT_IDLE: Idle line detection interrupt
  *     @arg USART_IT_ORE:  OverRun Error interrupt
  *     @arg USART_IT_NE:   Noise Error interrupt
  *     @arg USART_IT_FE:   Framing Error interrupt
  *     @arg USART_IT_PE:   Parity Error interrupt
  * @retval The new state of USART_IT (SET or RESET).
  */
ITStatus USART_GetITStatus(USART_TypeDef* USARTx, uint16_t USART_IT)