Recently, learning Chinese as foreign language (CFL) is becoming more and more popular around the world. However, promoting Mandarin among tens of millions of overseas Chinese has not been given enough attention. Research shows that language shift happens within three generations with minority immigrants (Fishman, 1991). Yet, less attention has been paid to how this process has actually happened. Based on the observation and monthly recorded data from eight families in Auckland, it has been found that, within 28 months after their arrival, the amount of Mandarin Chinese used at home is decreasing sharply; In terms of daily communication function, English is taking over Mandarin Chinese to express negation, greeting and gratitude; Parental interactive strategy also tends to be moving towards bilingual or even English. These are important signs of language shifting. Actions need to be taken for mother tongue maintenance.