BEIJING—Chinese e-commerce giant Alibaba Group Holding Ltd. cut its full-year revenue forecast by 4% to 6%, citing growing doubts about the economy as China’s expansion recently slowed to its weakest pace in nearly a decade.

Amid a trade row with the U.S., consumers are tightening their purse strings for some purchases. The slowdown is most likely to hit sales of consumer durable goods and Alibaba has already seen slower growth in consumer electronics, especially cellphones, said Vice Chairman Joe Tsai.