Lynn, who will also be competing in the GP2 feeder series this year, won the GP3 title in 2014.
Williams said his main role would be to help develop the new Mercedes-powered FW37 in the simulator but Lynn will also take part in a day of testing after the Spanish Grand Prix in Barcelona in May.
"Williams has a strong track record in bringing young talent though the ranks and our development driver position is designed to fully immerse new recruits into the inner workings of a Formula One team," said deputy principal Claire Williams.
"As a British team we are always on the lookout for emerging home-grown talent and Alex has caught our eye with his impressive performances in GP3."
Williams have Susie Wolff as their official test driver. The former champions have not named a reserve to race regulars Brazilian Felipe Massa and Finland's Valtteri Bottas.
The team finished third overall last season and are aiming for wins when the championship starts up again in Australia in March.
(Reporting by Alan Baldwin, editing by Sudipto Ganguly)
Share
