Louisa So was born and raised in Hong Kong.  She graduated from the Drama School of the Hong Kong Academy for Performing Arts and went on to join the Hong Kong Repertory Theatre as a full-time actress, where she was noted for her delicate performances and ability to play a wide range of roles.  So has featured in several notable productions including The Shape of Things, Between Life and Death, Love in a Fallen City and I Have a Date with Spring which ran for 100 consecutive performances and was made into a movie.  Her TV work includes Detective Investigation Files (I & II), Plain Love II, An Awakening Story, Misleading Track, Triumph in the Skies and Men in Pain.

So has won a number of awards and nominations including a My Favourite Drama Artist Award (Gold Prize) in the 1st Annual Artiste Awards; a Best Supporting Actress Award for Noises Off in the 2nd Hong Kong Drama Awards; and a Best Leading Actress Award for Between Life and Death in 2003 Hong Kong Drama Awards.  In 2006, she won a Best Actress Nomination in the 16th Shanghai Magnolia Stage Performance Award for her performance in Love in a Fallen City.

In 2009 she was awarded the Lee Hysan Foundation Fellowships by the Asian Cultural Council, which allowed her to spend 12 months in the United States.