Laura Petri was the daughter of lecturer Doctor of Philosophy Carl Magnus Petri of Halmstad, became an officer in the Salvation Army in 1902, but left in 1913 after serious disagreements, which she described in her autobiography Jag anklager, 1916. She devoted the next ten years to academic study. She graduated from the University of Gothenburg in 1919, completing a higher degree at Lund University the following year.
In 1921, she defended her doctoral thesis, Frälsningsarmen. Religionsvetenskaplig undersökning; however, it was rejected. She continued her studies in Germany and later in England, returning to obtain her PhD with the thesis Catherine Booth och salvationismen i belysning av religiösa frändskaps- och antagonistförhållanden, 1925.
Laura Petri wrote extensively, often using the pseudonym Soror; her works were characterised by social commitment and religious interest and include books of reports and the work Slumsystern, 1908, as well as biographies and novels.