Tim Cook, chief executive officer of Apple Inc., waves after speaking during an event at the Steve Jobs Theater in Cupertino, California, U.S., on Tuesday, Sept. 12, 2017.

Apple shares are surging so far this year as investors are bullish on the iPhone X product launch, but one Wall Street firm says the rally can continue through next year.

Citi Research reiterated its buy rating for the smartphone maker's shares Wednesday, citing several reasons why Apple stock will rise in 2018.

"While we acknowledge smartphone growth remains tempered, we continue to see positive tailwinds for Apple's fundamental growth drivers," analyst Jim Suva wrote in a note to clients.

Apple has crushed the market this year with its shares up 48 percent year to date through Tuesday, compared with the S&P 500's 19 percent gain.

Suva shared his five top reasons why the company's stock can go higher:

1. "Super upgrade cycle continues into FY18 as production issues have resulted in elongated lead times vs prior cycles, thereby likely to drive better than seasonal demand in March quarter."

2. "Tax reform benefit from reduction in corporate taxes and cash repatriation."

3. "Sticky User Base Which Drives Continued Services Revenue Growth ... continued momentum in mobile commerce, mobile gaming, mobile entertainment will continue to drive sticky services revenue growth."

4. "Enterprise Push Mid Term, Applewood Longer Term ... enterprises are spending more efforts to upgrade mobile device hardware which is positive for Apple. Longer term we believe Applewood (Apple's move to gain traction in India & more services) will eventually become material."

5. "Attractive Valuation – Shares are trading at a 20% discount to the SP500 in line with their 5 year median despite improving fundamentals described above."

The analyst reaffirmed his $200 price target for Apple shares, representing 16.5 percent upside to Tuesday's close.