According to the problem of hot-start in the BDS user terminal, a new hot-start method based on RTC punctuality is proposed. Local time is obtained by combining the punctuality through the I2C bus and the SOW analyzed by the D2 navigation messages. The positioning solution can be completed through obtaining the accurate launch time by the satellite capture tracking and Reading the effective ephemeris information. Compared with the TTFF of cold-start, the TTFF of BDS user terminal is significantly shortened, and the performance of BDS user terminal is greatly improved.