Two Estonian backpackers have been jailed for trying to set fire to the car of a strawberry farm supervisor in Western Australia's south while he and his young daughter were inside.

Kasper Kaokula, 26, and his brother, Kuldar Kaokula, were found guilty by a District Court of committing an act likely to endanger the life of Hassan Haidary, an Afghan who came to Australia in 2001 as a refugee.

Mr Haidary was a supervisor at a Denbarker strawberry farm, around 70 kilometres from Albany, where the two Estonians were working to refurbish buildings.

In February 2014, the pair parked their car across a remote road, and when Mr Haidary stopped to see if they needed help, they poured about two litres of petrol over the vehicle and tried to set it on fire using cigarette lighters.

Mr Haidary's three-year-old daughter was strapped in a car seat in the back of the vehicle.

Some of the petrol splashed onto Mr Haidary's clothes and into his eyes, but he managed to flee to his employer's farm while being chased by the men.

Judge Patrick O'Neal described the pair's crime as a "vengeful plan", saying they had "set out to lay a trap for their victim on a lonely country road".

Judge O'Neal said the victim had struggled to come up with an explanation for what the men did, but it seemed they blamed him after the girlfriend of one of the men failed to get a job in the farm's packing shed.

He described Mr Haidary as an "honest and decent man" whom he said had been "labelled a liar and worse" by the brothers at the trial.

Judge O'Neal said Mr Haidary and his family had come to Australia to escape from "people who wanted to harm him for no reason other than his religion and ethnicity".

"He believed the terror of their former lives was behind him but then you came along," he told the brothers.

"The realisation of what you were trying to do, would have been terrifying."

Kasper Kaokula was sentenced to six years and two months in jail, while Kuldar Kaokula received five years and eight months.

Both were made eligible for parole.

Taking into account time served, they will be eligible for release in 2019, when it is likely they will be deported.