Margaret is following in her father's footsteps in accepting the role which Percy held in 1985.
The show opens on Saturday at the West Midland Showground in Shrewsbury and will include a varied programme highlighting the bond between town and country.
There will be main arena entertainment, a comprehensive array of livestock classes, hundreds of exhibitors, children's entertainment and live music.
Margaret said: "Shropshire County Show is a true staple of the Shropshire calendar, and it is wonderful to be looking forward to a full schedule following the difficulties of the last two years.
“I am honoured to be president of the show and am very much looking forward to welcoming visitors both old and new to the showground on Saturday.”
Lance Jackson, chairman of trustees for the Shropshire and West Midlands Agricultural Society, said: “We would like to give a very warm welcome to Margaret, and we are extremely grateful that she has taken up the role.
“Margaret Thrower is synonymous with horticulture in Shropshire, and seems to perfectly fit the show’s theme of town meets country.
“Shropshire County Show is a celebration of our agricultural industry but also a very welcoming event for everyone whether they are from a generation of farmers or if they have never visited a farm in their life, there will be something for them here at the show.”
Livestock classes include heavy horses, in-hand and ridden hunter, veteran horses, Shetland ponies, children’s pony fancy dress and a qualifier for shire horses for this year’s Horse of the Year Show.
There will also be a wide selection of food and drink, art, clothing and other items available on stalls around the showground.
A flypast of a Second World War Hurricane will take place, weather permitting, and there will be music from Shrewsbury Male Voice Choir, the Wirral Pipe Band, Taiko Drummers, an opera singer and a ukulele band.
Other attractions include mountain bikers, mediaeval jousting with the Knights of Nottingham, a display featuring sheep, dogs and ducks, Ridgeside Falconry, as well as an outdoor gym.
Children aged eight and over will be able to try canoeing, and a kids zone will feature face painting, a juggler, wildlife show, monster truck ride and a magician, with many activities free-of-charge.
Tickets will be available on the gate priced at £20 for adults, £15 for concessions, and £5 for children over five, with younger children free.
For more information visit shropshirecountyshow.com