The Canadian had a difficult start to the season after he was injured in a cycling accident and had to miss the Bahrain test last year.
He spent much of the year trying to regain momentum relative to Alonso, who had a flying start with the team and logged a string of early podium finishes.
Stroll also had some reliability issues that struck him in races and also cost him valuable track time in practice.
However, he concedes that overall Alonso was simply the faster driver for the balance of the season.
"Some speed last year, for sure," he said when asked what was missing relative to the Spaniard.
"He was just quicker. So I have some ideas on where to work on, some things that I want to improve on, for sure, in that regard.
"And also, I don't like to use the word luck, but I think we had a lot of misfortune last year and I think that kind of made things more challenging.
"When we were fighting for good positions last year, there were a lot of races where we had technical issues. We had things just didn't go our way. So we want to just build on last year."
Stroll says that he's been looking at all areas as he tries to improve his form.
Source: Autosport