At the time that the Miao script was created, the A-Hmao language had no writing system of its own. Attempts had been made to write it using Chinese characters or to develop a Romanized transcription, but neither had met with great success. The A-Hmao did have a rich oral tradition however, including accounts of an ancient writing system which had been lost.

Prior to arriving in the A-Hmao community, Pollard had travelled extensively in southern China and had attempted to create scripts for some other languages in the area. These were never widely used, but illustrate his desire to make written language available to poor communities and speakers of minority languages.

In 1904 Pollard was approached by a number of A-Hmao speakers who had located him at great personal cost, wishing to learn to read. Pollard and his colleagues began teaching them Chinese characters, but realised that a simpler script would be more accessible to the preliterate A-Hmao. As they themselves became more proficient in the A-Hmao language, they realised it was syllabic, and, inspired by the success of the Cree syllabary created for a sociolinguistically similar community in Northern Canada, invented a new script for the purpose of teaching the A-Hmao to read.

Some historians and linguists, as well as many A-Hmao speakers, point to the highly patterned textiles produced by the A-Hmao and claim that remnants of the ancient script referenced in indigenous stories can be identified in these patterns. According to these accounts, the creation of the Miao script was aided by a number of A-Hmao speakers who had some knowledge of the linguistic derivation of the patterns. This belief is of great cultural significance to users of the script and played a large part in their acceptance of it.

Pollard and his coworkers went to great lengths to promote the script, establishing many schools and publishing a significant corpus of (predominantly Christian) literature. The impact was so far-reaching that an estimated half-dozen languages now use an adapted form of the script, notably the Eastern Lisu (Lipo) language.

After Pollard's death in 1915, demand for the script arose from other languages and dialects, and it was modified to accommodate these, as well as to better represent the A-Hmao language. One of the most significant modifications to the script was the representation of tone values by means of static tone marks, replacing the original representation of tone classes through the position of the vowel letters.

The form of the script which was in use in 1936 is widely used, largely due to a translation of the New Testament published that year. Further reforms in 1988 also yielded a popular form. The script is one of few minority scripts in the region which continues to grow both within the Miao dialects and also continues to spread into other language groups.