The?incidence?of?rare?diseases?is?extremely?low,?but?most?of?them?are?serious?and?tend?to?occur?in?childhood.? Mostly?they?are?caused?by?genetic?mutations.?Due?to?the?small?number?of?patients?and?low?market?demand,?the?research?and? development?cost?of?rare?disease?drugs?is?very?high,?and?only?less?than?1%?of?rare?diseases?have?drugs?available?for?treatment.? With?the?advancement?of?genetic?diagnosis?technology,?gene?therapy?by?virtue?of?its?"one-time?complete?cure"?feature?has? brought?hope?to?patients?with?hereditary?rare?diseases.?This?article?reviews?the?current?status?of?gene?therapy?for?rare?diseases,?and? discusses?the?application?and?development?of?traditional?gene?delivery?technologies?and?gene?editing?technologies?represented?by? CRISPR-Cas9?in?rare?diseases.