Katie was found with severe lacerations to her neck and chest on a playing field in York last month and died later in hospital.
Her funeral at the Minster will be led by the Archbishop of York, Dr John Sentamu.
Those attending have been asked by Katie's parents, Paul and Alison, to dress formally but with a colourful twist.
They said in a statement: "We are asking as many people as possible to attend and to wear traditional funeral outfits but to add a splash of colour such as a rainbow tie, red shoes, bright hair piece, etc., - whatever you feel comfortable in."
Katie's death shook the city of York after she was attacked in the Woodthorpe area on January 9.
More than 1,300 people donated money to an online appeal for her family which raised more than £25,000.
Her parents have thanked all those who have raised money and said a lasting memorial will be established for their daughter.
They said: "It has helped us more than you can ever imagine."
A video celebrating Katie’s life, containing photos of family occasions, has been posted on Facebook, along with details of a fund raising event next Saturday and a forthcoming “Concert for Katie music showcase”.
A spokesman for the family said: “They want her remembered as the beautiful little girl she is rather than the terrible circumstances surrounding her demise.”
The funeral service will be held in the Quire at York Minster with additional seating in the cathedral's Nave.
The funeral cortege will arrive at the South Transept Door of the Minster where it will be met by Dr Sentamu, who will receive Katie's coffin into the Minster.
After the dismissal at the end of the service, the procession will leave through the South Transept Door as the family leaves for a private family service of committal.
A 15-year-old girl, who cannot be named, has appeared in court charged with Katie's murder. She is due to appear at Leeds Crown Court again on Thursday.