A trusted family friend who committed depraved sex crimes against a young boy under his care has pleaded guilty to 130 charges in a Perth court.

Christopher Murray Harley-Townsend, 35, admitted in the District Court of WA on Friday to persistently abusing the then-10-year-old boy after the child's father – a longtime friend – invited him to live in their home in 2016.

Harley-Townsend, who wept in the dock as the charges were read, also admitted offending against two other boys and possessing about 12,000 images and recordings of child exploitation material.

Christopher Harley Murray-Townsend.

The court heard Harley-Townsend abused his 10-year-old victim on more than 30 occasions over a period of six months at locations including the family home in WA's Wheatbelt region and in a car on the way to a concert.