Abstract Due to the decreasing availability of fresh water to agriculture in many regions, saline water utilization in irrigation gets more and more attention. In order to facilitate the safe use of saline water for irrigation, the effects of salinity on crops should be understood, and optimal management strategies should be developed. A 3-year field experiment was carried out to investigate the effect of saline water on tomato yield and water use under mulched drip irrigation in North China Plain in 2003, 2004 and 2005. Five treatments of irrigation water with average salinity levels of 1.1, 2.2, 2.9, 3.5 and 4.2 dS/m in 2003 and 2004, and 1.1, 2.2, 3.5, 4.2 and 4.9 dS/m in 2005 were designed. Throughout tomato growing season, the soil matric potentials at 0.2 m depth immediately under drip emitters of all treatments were kept higher than −20 kPa and saline water was applied about 30 days after transplant. Results showed that irrigation water salinity ranging 1.1–4.9 dS/m had few effects on tomato yield, but had some effects on tomato seasonal accumulative water use, water use efficiency (WUE) and irrigation water use efficiency (IWUE). With the increase of irrigation water salinity, tomato seasonal accumulative water use decreased, WUE and IWUE increased. After 3-year irrigating with saline water, soil salinity in the 0–90 cm soil depths did not increase. So in North China Plain, or similar semi-humid area, when there were not enough fresh water for irrigation, saline water with salinity from 2.2 to 4.9 dS/m can be applied to irrigate field culture tomatoes after appropriate management strategies were adopted.